cell c has been a pain in ass for me

I have two contract phones with Cell c one ended in March but they continued debiting for both of them, and i haven`t been using the airtime and data loaded was suppose to do a sim swap but I did not now I called them to find out what`s happening they told me they will cancel the expired contract but they will still debit the full amount for the next two month I don`t understand why they do that ...cell c has been a pain in ass for me