They still charge you even after your contract has ended

I cancelled my contract with these guys at the beginning of the South African lockdown, however, they did not process it for weeks. As a matter of fact, it took me complaining on HelloPeter for any service agent to even give me a call about this cancellation. I finally got a call about 2/3 weeks later and the agent said she would cancel it, and she did on the phone. I was told that the money coming off my account in April would be the FINAL payment because we are billed in arrears every month. However, my account has just been debited again for something I don't even have any more and again I cannot get hold of these guys. Trust me, do not go with MTN and waste your time and money like this, these guys are absolutely useless and will never see any of my hard-earned money again.