******* Mtn Airtime contract in my name

I had a contract with them from 2016 and I paid faithfully until I finished my contract. I successfully closed my account but they opened another contract for airtime without my consent.

I told them to close it and I reversed payments withdrawn from my account with no authority. Only to find recently that they blacklisted me.This is unacceptable and I will report them on the ombudsman as I need this to be removed on my credit report.