Unauthorised upgrade by SummerSun Mobiles for MTN

With regard to investigation of ********** upgrade performed by Summersun Mobiles Services (Ref. No. *** ) on my MTN account number A*** (Phone no. ***). I have determined that I have been overcharged by more than R1700 by MTN as at end of January 2016 due to an upgrade not approved by my written signature and no device was ever delivered to me. This upgrade was done in June 2015 without my knowledge. I will be reversing the debit order deducted in January 2016 (1057.99) and December 2015 (1057.99) tomorrow (20/02/2016) to recoup incorrect deduction. My two cellphone contracts are not even open minutes / data contracts. I hope this issue will be resolved before the next debit order. How can a big company such as MTN allow a 3rd party to access my account without my approval and do a contract without my knowledge? I've been informed at the branch that this company does this ************ contracts on behalf of MTN. Once you MTN has determined the actual amount that I rightfully owe you (once all the ********** amounts I'm disputing is excluded), I will gladly settle it by EFT or debit order that you will re-initiate with me. Call me on ***