I’ll assume that this thread isn’t some sort of wind up , but PSTN is being switched off, that isn’t negotiable, all traditional telephony ( from BT ) will stop at that point, the replacement , DV , in effect requires a broadband connection, that could provided from the exchange (ADSL), from the cabinet (FTTC), or FTTP , the crucial point is that the phone instrument will not plug into a master phone socket, but will plug into the phone port of a broadband router, even if the copper pair is still used, as already stated , your existing copper pair line will handle a 0.5Mb as telephony needs a tiny amount of bandwidth, it’s the PSTN that’s being retired , not the copper pair network, although in time that to will be replaced by FTTP.
If you really paid an IT specialist, who told you your line is incapable of broadband , you wasted your money , whoever it was , did not have access to Openreach buildings, equipment ,lines or testers , so any opinion offered would be worthless, the fact that you won’t post your line prediction from the DSL checker , using your phone number , which is accurate, suggests you know you are incorrect.
Obviously being moved onto DV is optional, from the point of view , you don’t have to have BT or Openreach provide you with service , but if your ‘landline’ telephone service is from BT , it will , by the end of 2025 be DV .
