🚨 BT One Phone Shutdown - March 2026 - Switch Now

BT One Phone is being decommissioned in March 2026 — meaning your business telephony will stop working unless you switch. Read on to find out what You MUST Know (and What to Do Next)

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Why BT One Phone Is Being Withdrawn

BT haven't specifically said why they are withdrawing their One Phone service but our best guess is that it's too expensive for them to maintain and support. BT’s move reflects the industry-wide shift away from old analogue and legacy systems and consolidation toward digital voice services — voice over internet protocol (VoIP) delivered over broadband and apps. It's worth noting that these VoIP services are super high profit margin for providers but are known to be a lot less reliable than the services that they are set to replace with many customers expressing frustration and downtime during and after the switch.

Why This Matters to Your Business

If your organisation is still running on BT One Phone, your service will be switched off in March 2026. BT are retiring this platform as part of a broader industry move away from legacy phone systems and towards digital telephony.

This Means:

- Your existing BT One Phone SIMs will stop working after the cut-off date.
- You must migrate your numbers and telephony before the deadline.
- Leaving this to the last minute can disrupt your business phone lines, customer service, or operations.

Many businesses are already looking for modern alternatives. This is your chance to future-proof communications — without being tied to outdated technology.

Replace BT One Phone with ONSIM

BT One Phone is being withdrawn in March 2026. ONSIM is a modern, business-grade alternative that lets you keep your UK landline (and mobile) numbers and make and receive calls on your mobile — without PBX hardware, apps, or unreliable VoIP.

A Direct BT One Phone Alternative

ONSIM replaces BT One Phone giving you access to the same type of service, features and we even use EE's masts so coverage will be identical.

Fast, Managed Migration

We handle the switch from BT One Phone end to end. For compatible devices, we can also provide a SIM or eSIM so the transition is quick and seamless.

No Apps. No VoIP Instability.

Unlike app-based VoIP services, ONSIM operates at network level — via SIM/eSIM connected to EE's mobile network. That means consistent call quality, no app logins, and no dropped calls.

Keep Your Number, Long-term

Your business numbers are yours. You can port them to ONSIM today and, if needed, move them again later. ONSIM will never prevent you porting out your number to another provider.

6,500+

Business Customers

BT One Phone vs ONSIM

A simple side-by-side comparison for businesses needing to migrate before March 2026.

Feature	BT One Phone	ONSIM Virtual Landline
Service status	End of life (March 2026)	Available now
Real UK landline number (01 / 02 / 03)	Yes	Yes
Answer calls on mobile	Limited	Yes
Make call displaying landline number	Yes	Yes
Underlying mobile network	EE	EE
Native Call Recording	Yes	Yes - more advanced
Hunt Groups	Yes	Yes
Conference bridges	Yes	Yes
PBX or desk phone required	Often	No (but can be used)
Apps required	Varies	No (network-level)
Call reliability	Variable	Consistent
Number porting	Yes	Yes (managed)
Single Contract and Bill	Yes	Yes

BT One Phone is being withdrawn in March 2026. Migrating early reduces risk and avoids last-minute disruption.

Get a migration plan Explore ONSIM

FAQs

Frequently Asked Questions

Seamlessly migrating your services from BT One Phone to ONSIM.

How does ONSIM compare to BT One Phone?

ONSIM is the closest replacement possible to BT's One Phone service. We match nearly every feature including Native mobile dialling (no apps), custom forwarding, hunt-groups, landline caller IDs, call recording, reporting and more. We even use EE's masts so the coverage will be identical.

Are there any features ONSIM doesn't provide that we got with BT One Phone?

Yes. ONSIM do not provide a native management app (the BT One Phone App) - you can still make changes to your settings in real time but this is managed through a secure web portal. We also do not provide a managed directory service which was also included in this app.

Are there any features ONSIM provide that BT One Phone did not?

Yes, loads. - inclusive roaming in 39 countries (including USA), cheap international calls, Queues, Conference Bridges, API access, Black/White Lists, Full TOD routing, roaming controls, international numbers and multi-country support, SMS Gateway, Call Parking and much more.

Is ONSIM a cloud-based calling (VoIP) app?

NO! ONSIM is a mobile service just like BT One Phone - it doesn't use Apps or VoIP to make or receive calls but just like One Phone you can add IP phones and Apps if you wanted to.

Can I keep my existing numbers?

Yes. You can port your existing landline and mobile numbers to ONSIM from BT One Phone.

Can I make outbound calls showing my landline number?

Yes. You can display landline or mobile numbers when you call out - multiple users can even share the same number to dial out

Is call quality reliable?

Yes. Just like BT One Phone calls are routed over mobile networks and VoLTE not VoIP

How quickly can I get started?

We can set up your service instantly. Porting mobile numbers takes 24 hours and porting landline numbers takes 5-10 working days (this is the time taken to process the request by BT not downtime - your numbers will remain active during this period)

What does it cost?

We offer unlimited calls and texts for £10/user/month - various data packages can be added - full pricing is listed here. If you have a team of more than 50 users please reach out to sales@onsim.uk for a custom quote.

My BT One Phone contract runs past March 2026 — can I leave early?

Yes. BT’s decommissioning effectively supersedes the contract end date. Many businesses aren’t charged early exit fees when switching before the service is retired.

Will switching disrupt my current phone numbers?

No. We have a great deal (15 years) of experience porting numbers from BT and as a reputable provider we help manage the porting process for our customers every step of the way. This allows us to transfer your numbers with minimal disruption.