Contract Cancellation Issues

I am a very UNHAPPY client at this moment !!! My contract expired on the 12th of May 2022, i called in on the 1, 11 and 28 April to have this contract switched over to prepaid. I also asked numerous times if April would be my last R500 payment for device: *** and in all of those cases they confirmed yes, now my debit order has deducted AGAIN and my question is why ????? My payment for May was deducted in April ... So why must i pay an amount of R500 in May for June if i will not be receiving those benefits? The call centre is absolutely useless and pathetic at that!!! The staff at the call centres seriously need more training, on numerous occasions i asked for a cancellation letter and none of them could provide me of that, i still have 4 contracts with MTN and trust me as soon as they expire i will never ever be making this mistake again!!!!!