Why is MTN ripping me off?

On the 17th of May 2023 I called Mtn to cancel my contract as I was done with my 24 months and received this Ref no. *** as proof that my request to cancel was noted. Then immediately after the call I received the message below...

"Y'ello! Your contract is set to be cancelled on 05/18/2023..."

17 July 2023 I received Data and airtime top up as usual which was not supposed to happen as my contract had been cancelled.

23 June 2023 I called to enquire why I received my package benefits again when the contract should be cancelled. Also enquired if month end of June I will be expected to pay the usual contract fee as when I was paying for the phone or just for the data and minutes they reloaded by mistake as my contract is cancelled last month and the person said yes I will have to pay R420. I asked the person if the system doesn't show that I cancelled my contract on the 7th May and he said it does show that I called in to cancel but whoever took the call did not cancel it. I said to him since I have used some of the data and minutes they sent me which they shouldn't have, I don't mind paying for that but I am long done paying for the phone so they can't expect me to pay R420 for R30 airtime, 2GB and 500 free minutes.

After the above call, I received the message below...

"Y'ello! Your contract is set to be cancelled on 06/24/2023."

Which is similar to the sms I received when I cancelled in May and was now wondering who didn't do their job when I called in the 1st time to cancel.

24 June 2023 I received the sms below

"Y'ello! You're now on a prepaid contract. We're giving you R10 airtime to get you on your way. Please call 135 with any queries. Enjoy!"

I made a call again immediately after receiving this message to ask the consultant if this means we are now square because before the above sms Mtn took back the data and minutes that were left in my phone as I only used them 6 days and it was stil alot so I thought they were fixing their mistake and we were now square. Then to my shocking surprise the consultant said month end I must still pay R420 and this is after they didn't even let me finish the package benefits they expect me to pay for. Mtn, please level with me here, please break down the R420 I am expected to pay because you guys failed to do your job when I finished my contract and even after I called in to make sure it doesn't carry on.

I am posting this here because after laying an official complaint with Mtn on the same day 24th June 2023 via email, a week later(4 the July) I received this response...

"We apologize for the delayed response. Please note that your contract was cancelled on 24/06/2023 and you still need to pay for the invoice dated 17/06/2023."

I regret ever having a contract with Mtn, that after being loyal to them for so many years, renewing my contract over and over, this is the thank you I get just because I now want to be a pre-paid client.

BP. Mohitlhi