Repeatedly billed after car was sold

I sold my car complete with the Netstar equipment, but cancelled the policy with Netstar on selling my car in July 2014 .<br> Since then Netstart have been repeatedly deducted the monthly subscription fee, even though this was cancelled in by myself in July 2014.<br> I have many a Ref # on the number of times I have called them to credit my account with this money, but yet again they deduct from my account.<br> <br> I need this sorted out & my premiums credited to my account soonest.<br> <br> Tanya Hawthorne