Mtn
MTN made a mistake and wants me to pay

I entered into a contract with MTN in March 2012. They switch simcard in devices which resulted in a huge bill. They have taken in excess of R12 000 from my account and now claims R7000 from me for outstanding account. I have numerous letters written to them but we have not been able to resolve this, my only feedback is calls and SMS messages from attorneys threatening to blacklist my company. The contract offered a simcard loaded with 3gig data including a modem and a second simcard loaded with R50 airtime each month. The limit was set and any additional data or airtime would have to be bought. The simcard which was attached to the modem on deliver was the wrong one, this was the s/c loaded with R50 instead of the 3gig data. We were not aware of this until the services was suspended and after numerous calls and visits the lady at MTN Tygervalley discovered the mistake. I have been trying since November 2012 to resolve this matter and get my money back but with no luck only threats of blacklisting. I can sent you copies of correspondence, it is to long to fit in this space. PLEASE HELP