Challenges
Preparing for the PSTN switch-off
Analogue and ISDN lines retire on 31 January 2027. Every line still on them has to move, and your numbers have to keep working.
The challenge
Your phones may already be on a modern system, but the lines behind them, the alarm, the lift phone and the fax line often are not. When the PSTN and ISDN are switched off on 31 January 2027 those lines stop working, and the stop-sell means they cannot be replaced like for like. The job is to find every line, decide what replaces it, and move it without losing a number.
What we would do first
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Audit every line and number
The lines and numbers you have today and where each one goes, including the ones nobody remembers: alarms, lifts, door entry, fax and card terminals.
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Decide what replaces each one
Hosted voice, SIP or Microsoft Teams for the phones; a digital service for the alarm and lift lines; broadband or ethernet to carry it all.
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Port the numbers
Existing numbers moved to the new service so customers keep calling the number they know.
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Migrate before the date
ISDN and analogue lines moved to digital services, with each number routed to the right people and hours.
The services that apply
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Telephone lines and numbers
The numbers your customers call and the lines behind them, from geographic to 03 and 0800, and the move off ISDN and analogue.
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Hosted voice and SIP
Hosted telephony with auto-attendants, call routing and voicemail, or SIP lines for the phone system you already have.
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Microsoft Teams
Business calls inside Microsoft Teams, next to the chat, meetings and files your staff already use, supported by Odyssey.
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Business broadband
Business broadband without a phone line, from SoADSL and SoGEA to full fibre, supplied and supported by Odyssey.
A client who has been here
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Client story, Construction and quarrying
Dunhouse Quarry
A hosted Mitel system and SIP lines to sustain higher call volumes across sales and administration as the quarry expanded.
Read the story →
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Guide
The ISDN and PSTN switch off and its effects on my business
Analogue and ISDN lines are being retired. What that means for your phones, alarms and lifts, and how to plan the move to IP.
Read the guide →
Questions people ask
When is the PSTN switch-off?
BT and Openreach plan to retire the PSTN and ISDN on 31 January 2027. The date moved from December 2025. New analogue lines can no longer be ordered, so a line that fails now cannot be replaced like for like.
Will we keep our phone numbers?
Yes. Existing numbers are ported to the new service, whether that is hosted voice, SIP or Microsoft Teams, so customers keep calling the number they know.
Does the switch-off affect alarms and lifts?
Yes. Any technology running over PSTN or ISDN lines stops working, which can include alarm systems, lifts and door entry. Each one needs a digital replacement before the date.
Can we keep our existing phone system?
Possibly. If it supports SIP, we can connect it with SIP lines; if not, hosted voice or Microsoft Teams replaces it. Some legacy equipment can be kept with analogue converters.
Will our internet connection cope?
It may need upgrading so it has capacity for calls as well as everything else. We check what your address can get and recommend broadband or ethernet to carry it.
Talk to a human about the PSTN switch-off
Call and we answer within three rings. Or tell us what you need and we will call you back at any time.