Bad experience with a contract from mtn

i took a contract of 2 huawei Nova11i my monthly installment was R560 if i'm not mistaken,but the first month i had to pay R1,400.i paid it and went to the store to request the lady(toilet) who helped me to review my contract, then she said the mistake she made was to open my cellphone line to unlimited. Then she has promised that she has fixed the problem. But still the next month it was the same story, i paid again then went to the store to fix it but no it was not fixed. Then i stopped paying expecting them to call me to make an inquiry why im not paying.the did not,instead they blocked my number,and rushed to take me to credit berua ..
Run way from mtn