Cartrack cancellation process

I suggest that you do not take out a cartrack contract should you plan to cancel, without any hassle. I cancelled my cartrack contract and paid the full cancellation fee. I've been receiving calls everyday, twice or more a day, from the cartrack consultants requesting the oustanding payment of which I settled. Furthermore, the cancellation letter was incorrectly dated and issued to me a month after I requested the cancellation. And during this time, an outstanding amount accrued. This is ridiculous and a complete waste of my time.