Contract cancellation

I am trying to cancel my contract with MTN for the past 2 month. I don't have signal where we are living. A MTN technician came to our house confirming there is no signal and that MTN can't assist and that I can cancel my contract with them without any penalties as they can't provide the service to me as per the cellphone contract. He send me a letter confirming the contract needs to be cancelled without any penalty fees which I had to give in at my nearest MTN store. On 27 July 217 I gave in the letter and my cellphone and signed a notification that my contract needs to be cancelled and my number changed to pay as you go. Since then the contract has not been cancelled yet. I send MTN customer care an email every week to ask what is going on. The last communication I received is that they did not receive my phone and wanted to know at which store I gave it in. I rep**** to them that I did give in the phone at MTN Kollonade. I also visited the MTN store in Kollonade again and the sales lady Marileth confirmed that someone from MTN already came to fetch the phone on 17 August 2017. She showed me the confirmation. Still MTN hasn't cancelled my contract yet. At the moment I am paying for a phone I don't have.