Shady business especially towards cancelations.

Called in September to cancel a car I sold, they told me they work on 1 calendar month cancellation then referred me to their T&Cs which state "If you sell the vehicle, you must tell us at least three days before you hand the vehicle over to the new owner". I did that and they still charged me for the next month saying I was on a month to month. Now in October they are sending me another invoice for the car I canceled in September saying their system does not show any cancellation. Funny on the day I canceled the one car I mentioned the dealer installed trackers device on my car, they immediately tracked it and activated it but decided not to cancel the sold car probably because I complained about the calendar month policy for sold/******/written off cars. Also I asked for an email to complain and they gave me the other Tracker complaints email.