My mother has had the same landline number for 30 years and doesn't regularly use mobile. She's currently undergoing regular and extensive cancer treatment through the NHS, who have dropped the ball several times on appointments, sometimes by months, and changing her landline now would not improve the situation considering the frequency they have lost information. Not to mention extended friends and family use this number.
A year ago I arranged for her broadband + landline in my name, switching from BT to Plusnet. There was no issue keeping the same landline number. BT's website also says that a request can be made for new account holders (e.g. where there is a separating couple or bereavement) to keep the existing landline number. I no longer live at the address and to put it bluntly we don't know how long my mother has so it makes sense to be in her name.
I understand I cannot just switch account holder. But if I end my contract and my mother creates one with Plusnet, different Plusnet support staff differ in their stance whether the landline number can be kept? Online Chat say no, telephone staff so far say yes. We've had orders created being told this will work, then cancelled when the automated emails tell my mother she will get a new number? Can BT keep numbers in place when Plusnet cannot? It seems madness this cannot be achieved, e.g. for the examples BT give on their support site that I mentioned above?
Fixed! Go to the fix.
First of all I'm very sorry to read of the health problems your mother is going through.
If you're wanting the account to be in her name, the best way to do that, assuming the rangeholder/operator of her number is BT, would be to sign up at www.plus.net inputting the address only not the telephone number.
(Due to the way we work, we can't takeover our own line whilst keeping the number the same).
Once the order completes, we should then be able to renumber the line accordingly.
However, it's not guaranteed we'll be able to get the number back as once ceased it'll go into a pool of numbers where it can be picked up by another provider.
If you would like to go ahead, I'd recommend letting me know over here, so I can keep an eye on things and make sure we pick up her new account as soon as the order completes, renumbering the line at the earliest opportunity.
With that said, unfortunately even I can't guarantee something won't go wrong.
It's also worth noting that if you're still in contract on your account, there might be early termination fees applicable for breaking the contract early.
I hope this helps you though.