Miladys saying I haven't paid my account and I did.

I received a phone call on the 12 September 2022. 17:45 there around. I forgot to pay my monthly balanceof R770 I told the lady I will pay it now. Instead of paying R770 I paid R900. Now I am receiving messages I haven't paid, I need to pay by the 19 September 2022 and my account is being WATCHED. I tried to phone Miladys unfortunately they pich up the phone and put it down or they not answering. Please help me to resolve this issue. Thank you.