Cancelled contract but still receiving statements

I had a Cell C contract - ***. I settled the contract on 24 February 2015, paid R1487.58 (after calling the Retention department to get the settlement amount and the procedure that follows). Once I made the payment, I was told to call them 2 days after the payment was made to ensure it reflects. I spoke to the agent and she confirmed that they've received the payment and that the contract will be cancelled. Then I received a statement for April 2015. I went to the N1 City store - a consultant confirmed that the contract was still active and they were taking R199 (monthly installment) per month from the settlement amount. This had happened in March as well. She couldn't help me - as I had to call the retention dept. I did this about end of April and I was told the contract will be cancelled. I called the next day to confirm and I was told it was converted to a prepaid account. BUT I have received yet another statement for May. I've laid a complaint on Cell C's website on 18/5/15, received an automated reply, but still nothing. This is ridiculous - I closed my account with them for a reason - pathetic service!!