*****ulent charges from Netstar for non-existent contracts

Netstar has starting charging me again for contracts that were cancelled years ago. One contract was cancelled over 15 years ago when the car was sold! Over a year ago they suddenly started reprocessing the debit orders. When I had them returned by the bank, their collection agents started harassing me for non- payment. I spoke to several people at Netstar to explain the situation and no matter the promises the ******* debits and harassment continue. For another one of the cars I sold in 2016 and cancelled my contract they have continued debating my account *******ly for years inspite of me calling and advising them if the cancellation on several occasions. I then asked them what car they were tracking and they told me that they were not tracking any vehicle! They then started re-tracking this car which has has another owner. So they were charging for no service provided and then started tracking a car that belonged to someone else! I find their methods highly suspect and tantamount to *****! I cannot get anyone at Netstar or their dubious collection agents to resolve these matters for over a year now. Can anyone help?