let's clarify this...

the way i understand it, your problem is about practicality - you prefer to transfer phone line and dsl without cutting off the service.
as for the phone line, a change of owner is possible bec. as i said, i've done it before. in fact, in another case, when i decided to use my residential line in my business, i asked pldt if they could convert it to a commercial line with my separate business as the owner, pldt agreed without any cut-off in service. of course, i had to sign documents and a new contract for my business, same as when we signed new documents and a contract for the transfer of the house line in my first example.
as for the dsl, its possible that pldt will agree to the same thing with the phone line, and not cut off the dsl if the buyer will sign a new agreement. as in the case of the phone line, this will require a new contract between pldt and the buyer without cutting off the service, without any cut-off in the service.