billed for a cell phone that I do not have

I took out a contract with mtn during July 2012. The service were so bad that I had to go to their outlet every month to query. At some point I decided to await the contract to be finalised. I paid what I owed mtn and terminated my account end of July 2014. During september 2014 over R1000 was deducted from my bank account. I then made an enquiry on why I was billed. I was assisted by a lady called Nandipha ***. She told me that I had took out a new contract or upgraded my contract. I was told that I took a huawei and a tablet at cellular city in Joburg. I was asked for a copy of my Identity document and an affidavit stating that I never received any of the items. I mailed the documents to her but till this day I am yet to be assisted on the matter. I then decided to got to the outlet where I initially took my contract. I was assisted. And given ref usd ***. I have since been going back and forth on this matter but stil do not know how can someone take out a contract on my name. I get sms's that I owe mtn R12000 for this contract. I am not going to pay for services that I am not receiving. Account A***. #mtn must be closed this is unacceptable.