Crediting & billing a cancelled contract

I requested to cancel my contract on 9 December 2022 since you rejected my upgrade on cell *** Which the cancellation was not processed according to your agent, when I called again in February to enquire why I am getting billed for February. She then advised me that she has now processed my cancellation which I received email confirmation on the 7nth of February 2023 which my last bill date will be March 2023… But now I am confused as to why am I getting credited minutes, sms’s & data now in March and set to be billed again in April.L when I have already cancelled in February.

They must reverse all items I have been credited for March as I will not pay the bill for the number. Am so tired of the lack of services with MTN, am porting back to vodacom.