Debiting accounts without authorization

Tracker has these 3 years contracts when the contract comes to an end the don’t send you notification that it has come to an end they just continue to debit your account on a month to month basis without authorization. It’s been 2 months that they have been billing me for it, I called to ask why they claim they sent me an sms, which I didn’t receive in July. All SMS’s I’m receiving from them are to confirm that they conducted a test, now they refuse to give me my money back saying they sent me an sms which they cannot confirm receipt of it. Why do we still do business with ***** company’s only God knows, if I knew that this would have happened I would have cancelled my account with them a while back, I’m really upset by their treatment even with all the business I’m giving them.