Worst service provider!

We have been trying to cancel our contract since last year. Everytime we are guaranteed that the contract will be canceled - we just need to pay ONE MORE debit order. It's been a year now, and due to incompetence we still can't get this useless contract canceled and somehow our premium has doubled? We have now again called in a attempt to cancel this contract.. and again it's the same - we just need to pay ONE more debit order and the contract will definitely be canceled. The only extra this time is that we need to pay an additional amount for a "cancelation fee" which we are naturally unwilling to pay. This due to Cell c not doing their part and providing the most disgusting service I have ever encountered.