Cell Phone Contract upgraded without my consent

My MTN cell phone ends this month as the last payment on the contract is the 20th of March 2016. I have received numerous calls from MTN asking me to upgrade my contract which I have refused as I do not want another phone. On Saturday (05/03/2016) I was notified by MTN that my contract has been upgraded and my payment details have been updated. I have not requested for my contract to be upgraded (telephonically or at an MTN branch). I do not even know which phone or what kind of contract I have been **********ly entered into. This is a great concern to me as MTN Corporate delivers there cell phones to clients. I have called the MTN contact centre multiple times and spoke to Amanda Paladi (ref ***). Amanda informed me that MTN can only help me if I get an affidavit stating that I have not requested an upgrade and she could not give me any more information or the call recording. I find this to be ridiculous as this is a clear case of ***** by MTN employees however no one from the company is willing to look into the matter and find out who is responsible. This is by far the worse experience I have had with any company and the service I have received has been pathetic.