My contract with netstar ended a year ago but they kept on taking money from my account then I told them that I cancelled the contract but they kept on debiting

My contract with netstar ended a year ago but they kept on taking money from my account then I told them that I cancelled the contract but they kept on debiting.when I call their call centre to enquire then they send me from pillar to post .now they handed me over to debt collectors of which I dont owe them anything. I'm no longer even driving the car that has that tracker.