How can I get Tiscali to prove they still have an active CPS on a phone line

Spudgy

Problem is with a contract my other half had when she lived with the parents. She moved out and the parents changed the phone line to the Post Office. We set up a new contract with Tiscali for broadband and an additional charge they were making they said was for the faster speed broadband. Change in circumstances and I changed the payment to my bank account and cancelled all direct debits from my other halfs. Then she gets a letter saying she owes money for this phone line rental.

When she cancelled the account (2 years ago) she explained she wasn't in contact with her parents anymore etc etc. Have written to Tiscali and now emailed them as they reckoned they hadn't got the letter.

My question is how can I get Tiscali to go away as I don't believe they have the active cps on the phone line and so far they haven't been able to prove they have. To me this is an extortion racket........can anybody advise please?!