Contract Cancellation & Billing BLUNDER

My contract was due to end on the 10 Nov 2022, I had wished not to upgrade or proceed with the contract as MTN pricing is not favourable and the service is even worse. I went into the store on the 29th Oct to do the cancellation. In Nov when I called in to follow up I was told that even though the contract ends on the 10th Nov I am still required to serve 30days notice of cancellation . Absoultely absurd! Be needless to say I do it. I then call back in early Dec to confirm contract is cancelled , I am then told no it isnt because I now have an invoice for Nov for a line that is meant to be prepaid and for a line which we were not provisions any mins or data for . Again I do it and make payment . Me expecting that this matter is closed off. I called today for a statement as I have not recieved this for my other two lines and what do I find , again I have been billed for the line that was meant to cancel in Nov. Cancellation was only concluded by MTN on the 20th Dec - a delay that is not my fault as notice was given on the 29th Oct. After 45mins on the line now and being transfered between billing , cancelations , retentions and MTN direct I am put back to cancelations to correct the error and proceed to hold and listen to a fat conversation of an agent who is not on mute and isnt talking to me. I proceed to spend 5 mins saying hello hello hello and no response. Now I am tired of wasting my time and energy to call MTN . I will not pay for Dec and want the account corrected and neither will I go into the store or spend additional time speaking to individuals who clearly don't understand there own processes . FIX my account. I truly cannot wait for my remaining two accounts to come to an end so I can be rid of MTN