MTN Rectify

I added a new contract line with MTN in 2021 July and the salesperson who was assisting me advised that they have a special on the package I was taking, the deal was that I would receive a DATA line that is free for 12 months (meaning that I won't be paying for it) to my Suprise month end I got debited for two sim cards instead of one. I have been communicating with MTN personnel, but I am not getting any assistance and debit orders are still going off my account. I have proof of communications and relevant people I was communicating with. I