Yes it’s possible to have a new FTTP service installed by BT ( I say BT because you are posting on a BT forum ) without affecting your existing FTTC supplied by someone else.
ISP’s asking if you want to keep the current ‘line’ is (in my opinion) a little misleading as in effect those questions are referring to porting your phone number from your current provider to BT ( in BT case via DV ) , and as a consequence of that your entire service from the current provider will cease (in general terms ceasing or migrating the phone service, the associated broadband will also be ceased ) it would be better in my opinion to ask do you want a phone service , not a ‘ line’ or ‘landline’ .
If you want to maintain the current VDSL/FTTC service as it is with your current provider (I suspect that’s the case , very similar question being posed on another forum ) and have alongside it a new FTTP service ( broadband only ) , that is entirely possible, but needs to be ordered with no reference to the existing FTTC service , any sign up question regarding do you want a phone service with your broadband obviously you answer No (this should negate any question about do you want to keep your phone number ) , perhaps counterintuitively you answer No to do you want to keep your ‘landline’ as it’s really asking do you want to keep your phone number .
The basic thing you need to achieve is your old ISP not being informed of anything at all by OTS , this FTTP order having nothing to do with them , OTS (One touch switching) or strictly speaking TOSCo , the company behind OTS presumably couldn’t in visage anyone would ever require two competitors both supplying service ,and only switchers moving completely , so the questions asked aren’t particularly descriptive in cases like yours …answer the questions with the mindset of will this send a message to my old provider…no messages sent by OTS to your old provider, nothing changes with your old provider…the acid test is not receiving and ‘sorry to se you leave’ messages from the old provider, you may be a business user with your old provider but I’d still expect a communication if OTS says to them that you are switching , which of course you aren’t , you are having two discrete services , for the time being at least
