MTN billing for items not on contract

I took out a home uncapped FLTE 10 Mbps 400GB for R449 on the 12th of October 2022. As per my contract with MTN which I have provided them with and the allocated data as per my app, I have 400GB data allocated to me. After countless attempts to get an invoice from MTN, I was eventually able to obtain one today and I realised that I was charged for a home uncapped FLTE 500GB. This is in disagreement with my signed contract and highly ********* of MTN to be charging me for something they are not providing me with. I request urgent assistance in resolving this issue