Paid cancellation costs but contract not cancelled

I wrote to Cell C several times and phoned them to obtain cancellation figures for my contracts. They eventually provided them and I immediately paid the amounts. Now months later they have not cancelled my contracts and they say I am in arrears. In addition they want me to start the process again. Surely they have on record the cancellation figures provided and they can clearly see the deposits made match. It is not like I could have magically pulled those cancellation figures out of my head. They have not cancelled the contract when the payments were made in line with numerous requests and instructions. I should not have to suffer as a result of their inability to process and finalise a simple cancellation.