Can't cancel my contract and incorrect debit order going off after contract end date

I'm having the worst experience with MTN. I've been trying forever to cancel my data sim that is now past the contract expiry date. I stay on the line for longer than an hour waiting to get through to the retentions department. Eventually I give up. On top of that a debit order went off this month, past my contract end date. As if that's not enough, the amount taken off is not just the R299 that normally goes off, the amount is R1299 which caused another debit order to hop. It's now March and my contract ended in January. This is unacceptable. I won't sign up with MTN again.