The Telstra phone system sunset: three products, hard deadlines.

Three Telstra phone products. Three confirmed end dates. All aimed squarely at small and medium businesses. Still trying to make sense of the Telstra phone system sunset as a string of unrelated product updates? It’s a deliberate strategic withdrawal from a customer segment, executed across three separate product lines on staggered timelines. The products are different. Yet the pattern is the same.

For a broader view of SIPcity vs Telstra including pricing, contracts, and migration steps, see our complete SIPcity vs Telstra comparison guide.

Telstra phone system sunset: three products, one direction

Let’s put the confirmed facts on the table, because the full picture only becomes clear when you see them together.

• Telstra Business SIP closed to new customers on 30 May 2025. Existing customers remain on the service “until further notice,” which is not a guarantee of permanence. It is a holding position on a platform Telstra has stopped investing in. Business SIP was the workhorse for thousands of Australian businesses connecting an existing phone system to Telstra’s network over any internet connection, including non-Telstra broadband. That option is now gone for any business that does not already have it.
• Telstra DOT (Digital Office Technology) went to stop-sell on 30 September 2025. The platform shuts down permanently on 30 August 2027. No new services, no contract renewals, no address moves. Every remaining customer is on a forced migration path with a hard deadline. DOT was Telstra’s primary bundled phone-and-broadband product for small businesses. For many of those businesses, it was the only phone system they had ever known.
• Telstra Calling for Office 365 (TCO365) stopped accepting new customers on 1 November 2024 and withdraws completely by 30 November 2026. This product tied Microsoft Teams directly to Telstra’s network for voice calls. It was positioned as a modern replacement, and it is also now being retired.

That is three products, all targeting the SMB segment, all confirmed for retirement within a two-year window. The Telstra phone system sunset is not a maintenance decision. It is a portfolio decision.

Why Telstra is making this call

Telstra has not made a public statement describing this as an exit from the SMB voice market. But the facts of the portfolio do the explaining for them.

Business SIP competed directly with SIP trunking products offered by every other Australian carrier and a growing number of specialist providers. The margins on a basic SIP service, particularly for a self-service customer on a standard NBN connection, are thin. The customer service cost of supporting thousands of small businesses with diverse PBX configurations is not.

• DOT was a legacy of the pre-NBN era, when bundled voice and broadband over a single line made sense. The product required specific hardware, suffered from distance and line-quality issues, and tied customers into multi-year commitments that increasingly felt out of step with how Australian businesses actually buy technology.
• TCO365 was a Microsoft-first product in a market where Microsoft is no longer the only credible collaboration platform. It also depended on Telstra maintaining the SBC infrastructure, the number ranges, and the carrier relationships to make Teams-as-a-phone-system work. As Teams Phone has matured into a product Microsoft sells directly, the Telstra wrapper has lost its commercial logic.

It’s not in Telstra’s interest

Added to this is the broader cost of running carrier-grade voice for thousands of small customers: dedicated infrastructure, regulatory compliance, porting operations, fraud management, support staff, and the integration work to keep all three products operational on systems that are themselves aging. At some point, the per-customer cost of keeping these products alive exceeds the per-customer revenue, and the rational corporate decision is to stop.

What the Telstra phone system sunset means for affected customers

If you are reading this and you are on one of these products, here is what you actually need to know.

Telstra Business SIP customers can keep the service running for now, but the writing is on the wall. Treat your existing service as a bridge to whatever comes next, not as a long-term platform. Start your migration evaluation now, not when Telstra announces a final shutdown date. Your PBX, your handsets, and your number ranges can all move to a SIP trunking provider without disruption, provided you give yourself enough runway.

Telstra DOT customers have a hard deadline of 30 August 2027. That sounds far away, but a proper migration for a small business, including new hardware if needed, number porting, call flow configuration, and training, typically takes 4 to 8 weeks. If you have 50 handsets across three sites and CRM integrations, plan on 3 to 6 months. You have time, but not unlimited time.

TCO365 customers have the shortest runway, with full withdrawal on 30 November 2026. For Microsoft Teams users, the natural replacement is Teams Direct Routing from a specialist provider, which delivers the same Teams-as-a-phone experience without depending on a Telstra wrapper that is about to disappear.

Telstra phone system sunset: timeline at a glance

What to look for in a replacement provider

The Telstra phone system sunset is going to create a wave of switching across the Australian business market. Not every provider is going to be the right fit, so here is the short list of what to evaluate.

1. Number porting. Confirm that the provider ports your numbers for free and that the process is in-house, not outsourced to a third party. SIP trunking customers in particular should ask about porting lead times. 5 to 10 business days is the standard. If the provider is quoting 4 to 6 weeks, they are not actually doing the work themselves.
2. Pricing transparency. The published per-user price should include everything that matters: Australian mobile and landline calls, voicemail-to-email, call recording, auto attendant, mobile apps, and the basics of an AI receptionist. If the headline price is low but the feature list is short, you are looking at the same bundled-pricing model Telstra just walked away from, dressed up differently.
3. Contract terms. Month-to-month is the standard for any provider that is confident in their service. If the replacement requires you to sign a 24 or 36 month contract, ask why. Lock-in is a tax on uncertainty, and the uncertainty is all on your side.
4. Australian support. Confirm the support team is onshore, with a direct line to the engineering team that runs the network. Offshored tier-1 support with a script is the single biggest reason businesses hate their phone provider. It is also the easiest thing to fix by choosing differently.
5. Migration support. A good provider offers a phased migration, where you can move one site or one department first, validate the service, and then complete the cutover. If the only option is a big-bang cutover, the provider is asking you to take all the risk.

What happens to your phone numbers?

One of the most common concerns during the Telstra phone system sunset is whether you can keep your existing phone numbers. The short answer is yes, in nearly all cases.

Australian phone numbers are portable under the Telecommunications Numbering Plan. When you switch providers, the new provider submits a porting request to Telstra, and the numbers move to the new network. The process typically takes 5 to 10 business days for standard porting, with most providers handling the paperwork in-house at no cost to you.

There are a few edge cases to be aware of:

• If your numbers are tied to a specific Telstra product (for example, certain inbound-only numbers on DOT), the porting may take longer or require coordination with Telstra’s business team.
• If you have complex number ranges across multiple sites, the porting may need to be staged rather than done in a single cutover.
• If you have numbers that are part of a feature you want to keep (for example, a fax number), confirm with the new provider that the feature is supported before porting.

For most businesses, the porting process is straightforward and well-trodden. Reputable providers like SIPcity handle the entire process in-house, with no third-party porting brokers and no surprise fees.

Where SIPcity fits

For full disclosure: I work for SIPcity. We are a 100% Australian-owned VoIP provider, and we have been running the same Australian network for over 15 years. The Telstra phone system sunset is going to drive a significant number of migrations to specialist providers like us over the next 12 to 24 months.

I am not going to pretend that makes us the right choice for every business. But for the kinds of customers affected, specifically the SMBs on Business SIP, DOT, and TCO365, the fit is generally strong. We support businesses with existing PBX hardware, and we provide a fully featured cloud PBX for businesses that want to leave the hardware behind. SIPcity also has native Teams Direct Routing.

Number porting is free and in-house, with 5 to 10 business days as the standard lead time. Pricing is all-inclusive, with no itemised add-on stack. Contracts are month-to-month. And if the service does not work for you, you leave and take your numbers with you.

The broader picture

Carriers exiting segments is a normal feature of a maturing market. Telstra is not the first, and they will not be the last. The Australian SMB voice market is moving from a bundled-carrier model to a specialist-provider model. The transition is being driven by exactly the same forces that drove similar transitions in fixed-line data, mobile, and cloud infrastructure: scale economics, technology commoditisation, and customer expectations of transparent pricing.

If you are a Telstra customer on one of the affected products, the practical question is not whether to migrate, but when, and to whom. The longer you wait, the more compressed your migration window becomes, and the less leverage you have on commercial terms. Starting the conversation now, while you still have a working service to fall back on during the transition, is the rational move.

The Telstra phone system sunset is not good news for the affected customers, but it is the market telling the truth about how SMB voice is now delivered. The providers that survive the transition will be the ones that have built specifically for this market, with the right economics, the right technology, and the right support model. That is a much smaller pool than the carrier-led model ever suggested, and the customers who pick from that pool early will have the most options and the best terms.

Frequently asked questions

What is the Telstra phone system sunset?

The Telstra phone system sunset refers to Telstra’s planned retirement of three business voice products:

• Business SIP (closed to new customers 30 May 2025)
• Telstra DOT (shuts down 30 August 2027)
• Telstra Calling for Office 365 or TCO365 (withdraws 30 November 2026).

All three products target the Australian small and medium business market, and the retirements are part of a coordinated withdrawal from the SMB voice segment.

Will my Telstra phone numbers be lost?

No. Australian phone numbers are portable under the Telecommunications Numbering Plan. When you switch to a new provider, the provider submits a porting request to Telstra, and your numbers move to the new network. The process typically takes 5 to 10 business days, and most providers handle it in-house at no cost.

How long do I have to migrate?

It depends on which product you are on. Telstra Business SIP customers can continue using the service until further notice, but should plan to migrate proactively. Telstra DOT customers have a hard deadline of 30 August 2027. TCO365 customers have the shortest runway, with full withdrawal on 30 November 2026.

What should I look for in a replacement provider?

Look for transparent all-inclusive pricing, month-to-month with no lock-in contracts, Australian-based support and onboarding, and a phased migration option. Avoid providers with no onboarding, advertise low base prices with extensive add-ons, or require 24 to 36 month contracts.

Next steps

Start your migration evaluation now while you still have a working service to fall back on. For a comparison of SIPcity and Telstra across pricing, contracts, support, and migration, see our complete SIPcity vs Telstra comparison guide.

See our Telstra TIPT alternative guide, our Telstra Business Voice alternative guide, and our Telstra DOT alternative guide for product-specific guidancance.

For a confidential discussion about your specific migration needs, contact our Australian team and we will walk you through the options.