As per subject line house rented and previous tenant hard to track down. Currently a dial tone so have an existing number. New people wanting a Vodafone naked DSL connection. But existing services on line. Any suggestions? Get a new line connected independent of existing but at what cost?
Submit a connection request with your chosen provider, in this case vodafone, they will see the live connection there and advise you to ring them from it, once you have called them from that active line they are able to submit a disconnection request regardless of the provider it is currently connected with, and can then proceed with the connection as per normal.
There are simple processes to resolve issues like this.. Contact your ISP and they should be able to get it sorted out for you.(Escalate if the help desk cannot help you).
Also Try dialling 07 832 0000 (Free Number) and see who the toll provider is (normally it will tell you) and usually its the ISP as well and dial 1956 and then ring up the ISP and tell them the old owners moved out and for them to disconnect the line.