Vodacom misleading Sales Rep, and failed Debit Order due to a bad cancellation process that would not debit the correct new amount

I have spent a tedious amount of time with Vodacom trying to sort out this issue, but still to the end I get problems cancelling my package.

Background : I decided to upgrade my account to a data package in December (despite having several issues with Vodacom with my account last time). On the call with the sales representative, I asked whether my airtime per minute rate for calls would stay the same when going unto this new package ( 0.79c per minute or so) and he told me that it would. I asked again and he said yes. I upgraded to the data package then.

Months later, I found out that calls are draining my airtime much faster than expected and I was in fact NOT still on that price per minute plan (I don't make a lot of phone calls, but when I need it, I need it). I called Customer Service to sort it out. They couldn't help me. They apologized that I mislead by the Sales Rep, but my options were very few. I decided that I will cancel the plan. I went through the process and explained what happened with the Cancellations Representative. She also apologized that I was mislead and helped me with the cancellations. She specifically stated it would only cost me the outstanding amount for that month (which I can understand). She also said I can pay the amount at a Vodacom Store or via EFT and I had 24 days to do so.

A few weeks later I went in-store and paid the amount. The person at the store said the account should be updated within 2 hours. Great.

Skip ahead after the weekend of the 1st, my account gets debited for the full amount of the Vodacom Debit Order, and it fails to go through. Why? Because Vodacom said it would be cancelled, so I believed them and thought the Debit Order would be fixed.

Skip forward to today, I called a Support Representative AGAIN, and I try to explain the situation to her. She keeps explaining that the Invoice was already generated, thus the debit order was unchanged (which is fine, it's not her fault). This doesn't make sense in my mind, as I already paid the cancellation. Why ask me to pay the "cancellation" amount and give me 24 days if you're just going to debit my account for the normal amount anyway?

I asked if she could point me to someone that could help me, but she was not sure who, so I gave up. I'm tired of this happening all the time.

This failed Debit Order will show on my record for the next 5 years. Just because of the bad communication/system.

(BTW, there was no suggestion from anyone to help me regain the airtime I lost, due to being mislead by the original Sales Representative).