After having a digital voice phone line and fibre broadband with BT since 2020 my phone line stopped working on the 15th March 2022. In registering the fault I was told the line would be back later that day. The line come back 2 hours later but unknown to me until the 4th April, in the reactivation BT had stopped the old number (which I have had for 30 years and use for business working from home) and given me a new number without telling me. On letting BT know on the 4th April I need my old number back, the new number has also been stopped and numerous phone calls since have still not resolved the issue. I have not had an incoming phone line since the 15th March and the earliest date I have been given for reactivation is the 4th May. 6 weeks without a line. Not good enough.
If you are using you line for business, then you really need a BT Business line, as a residential line does not cover business usage. Business users get a faster repair time, and can claim for lost business.
Its not always possible to get your old number back, but if it was originally issued by BT, then it may be possible, but saying that you need it back for your business, is not going to go down well with BT Retail.
What BT broadband package do you have?
I have Full Fibre 100. When I switched to BT Fibre (from Virgin) in December 2020 I was told I would need a new number if I wanted a Business account. I have had my old number for 20 years plus so did not want a new number.
Not sure why BT Business would insist on a new number, as although they are a separate part of BT, they use the same infrastructure. It makes no sense to me.
People have moved from BT Retail to BT Business in the past, and kept their number. That is assuming your original number is actually owned by BT, and not Virgin Media. If it was issued by VM, then you have no chance at all.
If you are a registered business at your address, I would be inclined to have a chat with BT Business sales and tell them the phone number that you must have for your business, especially if you can give them proof, i.e. printed stationery. See what they say, as there is no harm in asking. But it must be a BT owned number.