Cellphone contract

On the 22nd of November 2023 a consultant with the surname "Ncobo" phoned me from MTN telling me that there has been some changes on the packages I chose from MTN meaning that instead of receiving 2GB every month I will then receive 20GB with an addition of R20. No other amounts were confirmed, only R20 I was told of. Now to my surprise the statement says I have to pay R855,01. I will not pay for the amount I didn't agree to, I believe calls are recorded for matters like this. Let that agent pay it and revert to my package of R548.

Can MTN deal with their agents so that our credit records are not messed up because of their incompetency.