Tracker refuses to cancel

My mother-in-law sold her car in May. Cancellation request was sent on 27 May and followed up on 2 June again. 5 calls to call center and each time told was in process. Nothing happens and on 1 July debit order goes off. Every time I call the call center to resolve get cut off or call center agents laugh or pretend they have nothing on record. This is clearly a **** and they never assist in cancelling the contract! Account number ***. I have lost count of the hours lost trying to get the staff at this company to just do their job!