MTN Fourways Mall Franchise

I have had the worst experience in 30 years of doing an early upgrade. I did my early upgrade at MTN Fourways Mall with Mpho, and the manager, Francina. Mpho assured me that as per the system I was allowed to do an early upgrade. I took the 3 year deal where one hands in your old cell phone as well. I asked her how much the first bill would be due to the early upgrade and she said she was unsure and would let me know. I was then told to sign the 3-year contract. I asked if my debit order would still be the same as before and she said that it would and that the early upgrade just adds on the last few months to the contract. One week later a bill of R4 300 was debited. I have been battling for her to get this sorted out and no-one is assisting. Today she tells me that I agreed to a debit order of around R3 000 and that I signed for it. I would never in a million years sign for that amount. I am disgusted by the shocking service I am receiving from MTN. I would like this to be sorted out immediately, otherwise I am going to the owner of the franchise.