Modo MTN contract **** operation

This company is dishonest. I took MTN LTE contract through their agent in September 2021. I was told that monthly charge is R99.00. I read through the physical contract but it did not state the price. Then they charged me R199.00 per month. I called them and they investiagted the matter to which they admitted that agent said it's R99.00 per month and not R199.00. The contract was canceled but they blacklisted me because I refused to pay the incorrect billing. MTN's legal department is not helping with anything.