impossible to cancel contract

what a joke! my contract expired on the 14th of May, i had been enquiring at Mtn greenstone branch since April for procedures to cancel my contract, I have been told 4 times by different consultants that I should call on the day of 14th of May 2015, on the day it expires to notify MTN for cancellation. I remember I needed to give a 30 days notice, I did not trust the consultations and called the call centered, waited for about 40 minutes for someone to answer (by the way, very complicated JUST to find a number to CANCEL), I thought cell c was bad at ********! nevertheless, the call center advised the same thing. I then wrote a letter to MTN as a notice of cancellation on the 4th of May 2015, so I have a written proof. On the 16th of June 2015, I received reply from MTN that the contract has been cancelled via email, interesting enough I am still getting BILLED, and I received NO airtime LOL. I want my money back! I have given all the notices, why are you still deducting money? I stopped receiving my airtime from the contracts already! What a ****!! Please reverse my debit order or I will get my bank to do it.