Charging for no service

After more than five years paying faithfully I cancelled my Cartrack service as my insurer no longer requires my car to have a tracking device. Cartrack call centre agent said they require twenty working days to ‘cancel’ the subscription. Why so long ? I was advised my subscription will terminate in mid November. But they debit my account on the 5th of each month in advance in full and won’t provide me a pro-rota refund for the half month of November when the subscription is over. This is contrary to the Consumer Protection Act (unfair term). I disputed this and asked for a supervisor (busy) and asked for the supervisor to call me back. Still waiting. Come on Cartrack it’s not a lot of money but why charge for something you are no longer providing?