Incorrect Billing by MTN.

I took on another contract with MTN in February, ( I have never experienced such a problem with my other existing contracts) it was a Laptop package. I took up the contract at one of the MTN stores in Mimosa branch Bloemfontein. I was charged twice the agreed amount, I realized this before my 1st installment went off and went to report it, this was early in March. The issue still persists, I have sent emails to complaints management but my issue persists and It has now led to my account being in arrears something I tried so much to avoid. I am so disappointed with the entire MTN team and how they handled this quiry. As I write this there is anyone working on this matter to assist, I assume the branch manager who logged this ticket has given up on it as well, I'm hoping to be assisted. I'm approaching 4 months now with the same billing issue.