impossible to deal with Netstar

Netstars call centre and management is useless. Might just as well talk to thin air. I had to have the transponder in the car replaced as after 10 years it stopped working. I did not ask for a new contract, just for the transponder to be replaced. Shortly after I sold the car , took out contracts on the new car and cancelled on the old. However they refuse to cancel unless I pay cancellation fee. The matter has been "escalated " to management 2 or three times now with a promise that "management " will resolve the issue. Obviously management is non existent as precisely nothing happens in terms of a follow up. I am now cancelling my netstar debit order each month until the matter is resolved. Then will cancel with netstar on the new vehicle as well because dealing with a company like this is just impossible.