Ignoring the fact that you have been paying way more than necessary presumably for years , it’s true if you want BT to continue to provide telephony, you can’t have broadband from another supplier on the same ‘line’ ……assuming you want BT to continue to supply your telephony it is join BT for both services, or you can leave BT completely .
FYI as BT are providing the primary service (the telephone service) on your SMPF line ( shared metallic path facility ) with the broadband company delivering what is considered to be the secondary service ( this isn’t a judgement on how valuable to you each service is , it the order of priority when it comes to SMPF ) you need to decide what you want and tell your providers.
Do nothing BTW , you will probably be converted to a BT PDPL ( a transitional phone service that doesn’t rely on PSTN but isn’t Digital Voice either ) and your other providers broadband will be removed, so you need to do now what you should have done years ago , and make a decision about who you want as your single supplier, you can’t have two providers any longer , SMPF cannot exist after Jan 2027 and will be pulled before then , hence the notification .
You can move telephony to a third party VoIP provider and use broadband from BT or anyone else that will supply it , the removal of two services on one line refers to SMPF which is what you have , third party VoIP maybe what Google was referring to , or perhaps it was just wrong.
