In these troubled times there seems to be a danger of customers being cut off abruptly through no fault of their own.
It seems to me that being able to communicate on-line with your ISP's Customer Service but with no other services available might be useful in these and similar circumstances in the future.
As I understand it you can have an account with no services for some time, so is it even remotely possible for an ADSL level logon to be provided that would give access to the Member Centre login but to no other service, something like the BT test domain but providing a link to Metronet/Plusnet ?
Any customer finding themselves excommunicated could replace their normal ADSL logon Username/Password with a generic or personal fallback Username/Password and start negotiations with the ISP ( Contact Us ?) but do nothing else. Sort of cut off but not completely cut off, at least not until you came to blows.
Please appreciate that this is offered from a position of deep ignorance of the technology at that level and of course there's always the phone or perhaps someone else's PC and Internet connection. Maybe the idea is a bit more Metronet than Plusnet, is open to abuse, too embedded in the BT area to be feasible, too much work, too expensive, . . .