Horrible experience with Netstar

I sold my car in 2019 and informed Netstar about that. I understood that I had a choice to settle the contract or continue with the monthly premiums... no problem, I continued with the premiums. I kept getting travel logs, calls and texts about the car even though I informed them that I had sold it. I kept checking with them if the account is in order and also send notices for cancellation once the contract ends. My contract ended in November 2020, but Netstar kept debiting. Now some collection companies keep calling me on behalf on Netstar and want outstading monies... claiming that I never cancelled.

surprisingly, whenever I called, they would transfer me to another line which doesn't get picked up. Their customer service agents are rude by the way. I sent numerous emails to cancel but never received a response.