210gb contract for R599 billed for R1216.52 per month

I signed up for the 210gb data contract for R599 per month on the 26/09/2019 and received a pro- rata data, in October i received the full monthly allocation data for the month however when i checked how much is my first billing for the month, to my surprise MTN has billed me R2213.50 for a data contract advertised for R599 per month. I tried querying this (5 times)via the call centre and in the store with no luck, i even emailed a copy of the contract to a call centre Champion ( Sindisiwe Khaba) which clearly stipulate R599 per month, but still no luck to correct this error, instead what the agent confirmed to me is that MTN is actually and in fact charging me R1216.52 per month for a contract which is advertised for R599 per month for 210gb. I have a contract for R599 per month and i can also see on the MTN app that I actually billed R1216.52 per month and no one seem to know how to correct and resolve this.