Billing query

I received call on 12/06/2024 from Mtn consultant offering. Better offer according to him.the deal was for R100gb for R299 per month.So now they overcharged me since the day of activation. I went to MTN store at Mall of the north L5 for assistant on my account.when they check on system they found that SUL was never set since that day of activation.So thsts why my bill was high . As a customer I did not knew about the process the only thing that I knew was I going to pay R299. So I request the refund into my personal account from time they starts to debits. Sul was set today dated 23/10/2024 at MTN MOTN Account no BA*** Cellphone no ***