Voice and video
Telephone lines and numbers
The numbers your customers call and the lines behind them: local, 03 and 0800 numbers, porting from any provider, and every ISDN and analogue line moved to a digital service before the switch-off.
Who it is for
Every business in Teesside and the North East with a phone line on the old network: ISDN behind a phone system, an analogue line for a fax, a lift, an alarm, a door entry panel or a card terminal, and the numbers printed on the van and the letterhead that have to keep working. Also any business that wants a memorable 03 or free 0800 number, or to bring numbers from an acquired business under one roof.
What you get
Every line and number found, including the ones nobody remembers, each one given a digital replacement before the PSTN and ISDN are retired on 31 January 2027, and your existing numbers ported so customers notice nothing. New local, 03 and 0800 numbers supplied and routed to the right people and hours, delivered over hosted voice, SIP trunks or Microsoft Teams, and managed by the team that answers your calls within three rings.
The problem
The analogue and ISDN network is being switched off, and every line still on it needs to move. At the same time, the numbers customers know have to keep working.
BT and Openreach retire the PSTN and ISDN on 31 January 2027. The date moved from December 2025, and the stop-sell has already happened: no new analogue line can be ordered, so a line that fails now cannot be replaced like for like. Your phones may already be on a modern system, but the lines behind them, and the alarm, the lift phone, the fax and the card terminal, often are not. Anything running over a PSTN or ISDN line stops working on the date.
The job starts with an audit: find every line and number, decide what replaces each one, and move it without losing a number. Phones move to hosted voice, SIP trunks or Microsoft Teams; alarm and lift lines move to a digital service designed for them; some legacy equipment can be kept with analogue converters. The internet connection carrying it all may need upgrading so calls are not the first thing to suffer.
The numbers themselves are an asset. Existing numbers port from most providers; new geographic numbers give a local presence in a town you serve; 03 numbers cost callers the same as a local call and are included in most bundles, including from mobiles; 0800 numbers are free for callers. Dunhouse Quarry's lines went from ISDN to SIP as part of its hosted Mitel system; Country Valley Foods kept each site's numbers and knew which one a caller had dialled after consolidating onto one site.
What Odyssey provides
- An audit of every line and number you have today and where each one goes, including alarm, lift, fax and card terminal lines
- Replacement of ISDN and analogue lines with hosted voice, SIP trunks or Microsoft Teams calling before the switch-off
- Digital replacements for the lines that are not phones, and analogue converters where legacy equipment must stay
- Porting of existing numbers from any provider, so customers keep calling the numbers they know
- New local geographic, 03 and 0800 numbers, routed to the right people and hours
- Management of your numbers afterwards, with changes made by our service desk
What is included
| Included | Detail |
|---|---|
| Audit | Every line and number, where each goes, which carries something other than a phone, and who supplies it, written down before anything moves |
| Plan | A digital replacement chosen for every line, the order they move in and the dates, around your contracts and your operations |
| Numbers | New geographic, 03, 0800, 084 and 087 numbers supplied, and existing numbers ported from your current providers on agreed dates |
| Migration | ISDN and analogue lines moved to hosted voice, SIP trunks or Teams calling; alarm, lift and door-entry lines moved to a digital service; converters fitted where legacy equipment stays |
| Routing | Each number directed to the right people, teams and hours, with changes made by our service desk |
| Connectivity check | Whether your internet connection can carry the calls as well as everything else, with a recommendation if not |
Not included, or sold separately
- The phone system
- Hosted voice, SIP trunks, Mitel and Microsoft Teams calling are the services the numbers run on, each its own service
- Call charges
- Calls are billed separately from the line or number rental
- Alarm and lift service contracts
- We replace the line; the alarm or lift company confirms its equipment works over the new service, and we coordinate with them
- The internet connection
- Business broadband or a leased line to carry the calls is a separate service
How it is delivered
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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. We check the bills, the comms cupboard and the building, because the lift phone is rarely on anyone's list.
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Decide what replaces each one
Hosted voice, SIP trunks or Microsoft Teams for the phones; a digital service for alarm and lift lines; converters where legacy equipment must stay; and the connection to carry it all, checked for capacity.
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Port the numbers
Existing numbers moved from your current providers to the new service on agreed dates, in an order that fits your contract end dates and notice periods, so you are not paying twice for longer than necessary. Porting usually takes 10 to 20 working days for single numbers, longer for ranges and multi-line numbers.
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Migrate before the date
Each line moved to its digital replacement and tested, with the alarm and lift companies confirming their equipment on the new service, and the old lines ceased only when the new ones are proven.
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Manage the numbers afterwards
New numbers, re-routing, opening-hours changes and a number for a new site handled by our service desk, answered within three rings.
Why trust Odyssey with this
-
1987
Business telephony specialists since 1987
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3
Calls answered within three rings, and a director is always reachable
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In-house
All work completed by Odyssey employees, never subcontracted
- Delivered over our own business-only core network
Client story
Country Valley Foods
Two sites became one, with hosted Mitel telephony, cordless handsets across 36,000 sq ft and microwave internet.
Read the story
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.
Can we keep our numbers when we move?
Yes. Numbers can be ported from most providers, so customers keep calling the numbers they know, and we audit every number first so none is missed.
Does the switch-off affect alarms, lifts and card terminals?
Yes. Any technology running over PSTN or ISDN lines stops working, which can include alarm systems, lifts, door entry and card terminals. Each one needs a digital replacement before the date, and we coordinate with the alarm or lift company.
Do we have to replace our phone system when ISDN goes?
Not necessarily. If your existing phone system supports SIP we can connect it with SIP trunks; if not, hosted voice or Microsoft Teams calling replaces both the lines and the on-site system. Some legacy equipment can be kept with analogue converters.
What is the difference between 03 and 0800 numbers?
0800 numbers are free for callers. 03 numbers cost the same as a call to a local number and are included in most call bundles, including from mobiles, so they suit a business that wants one national number without charging its callers.
Can we have a local number for a town we serve?
Yes. We supply local geographic numbers for the areas you serve as well as 03 and 0800 numbers, so you can choose the mix that suits your customers, and route each one wherever the calls should go.
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 business broadband or a leased line to carry it, with a 4G or 5G backup where the phones cannot be allowed to stop.
What can our numbers run on once they move?
Odyssey Voice (hosted telephony), SIP trunks into a phone system you already own, or Microsoft Teams calling, and Teams Connect lets Teams users and Odyssey extensions call each other if you use more than one.
Challenges this helps with
- Preparing for the PSTN switch-offWhat changes in 2027, and what to do first
- Switching from an unresponsive supplierA managed handover, without disruption
- Relocating or opening a new siteConnected on day one
- Moving your phones to Microsoft TeamsCalls in Teams, on the numbers you know
- Bringing an acquired business onto your systemsOne set of systems and one supplier
Related services
Ask about telephone lines and numbers
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