There has been a few similar posts recently , presumably BT are currently in the process of moving BT customers like you , on what’s called SMPF (shared metallic path facility) that’s where two providers share the same cable to deliver separate broadband and telephone services , from the PSTN telephony ‘ network ‘ and onto a different telephone system, this requires you being moved off SMPF in advance of the PSTN telephony switch off , you can’t have this arrangement once PSTN has been retired, and the replacement telephone system can’t have a different company’s broadband service on the BT telephone ‘line’ .
TBH , the other examples of this , the other companies broadband is simply removed by whoever supplies it and the BT telephony becomes a PDPL (pre digital phone line ) so after the change there is no broadband anymore just telephony…as you are with two BT Group businesses (BT and EE ) your situation may a little different in that you are being asked if you want to join BT to keep a broadband service with your BT telephone service.
If you join BT for broadband in addition to BT telephony, you will get moved off PSTN onto BT DV (Digital Voice) telephony (and not a PDPL ) and that requires you to use the BT router as BTDV uses the BT router , if you don’t want BT broadband but do want to keep VT telephony, you need to advise BT and your telephone only service will be a PDPL .
