Mtn debiting incorrect higher amount from my bank account

I went to the store to upgrade my current mtn package. The experience in the store was good , the consultant was helpful in providing the necessary info that i needed and i chose the package that was best suited to me. I chose 5gigs for R199.99 per month. I signed the documents that the consultant gave me and he said that he will fill in the blanks at a later stage. i didn't think anything of that during the exchange. he did say that the first month f the new contract they would be extra admin charges etc. i expected this so i was not surprised when R739.00 was deducted from my account. however the second month of the new contract R739.00 was deducted from my account again. When i emailed them . a consultant asked to send through the contract. but i knew that only my personal info and signature appear on the contract and none of the new contract details appear on it. the second response to the contract was that i need to go to the store personally and speak to the consultant and get him to rectify my contract. I really don't see why i have to this , Im not the one that didn't follow procedure. why should i go all the way to the branch to correct someone else's mistake. Please do help with a submission to them on my behalf

thank you fatima