MTN money hungry

I have a contract with MTN and changed my debit order, in the first week of April, from 25th to the 1st. Despite having this on their system, I got an email today threatening suspension of my account. When my salary hit my account earlier than expected (I now only get paid on the very last day of the month hence the need to update my debit order dates) MTN couldn’t wait to get their piece of the pie. Of course this is course for concern for the coming months so I immediately jumped onto call with MTN to resolve this matter. They confirmed that the system shows my debit order date is for the 1st. So I questioned why I got an email threatening suspension of my account and why did they debit order my account before the 1st if the system correct reflects my preferred debit order date? The response that I got was that because I only changed my debit order date in the 1st week of April I will still be debited on the 25th of April and then again on the 1st of May. This is insanity! How can you make me pay for the month of April on both the 25th and then again on the 1st? It seems even MTN customer care does not understand their own payment process. I asked to speak to a manager and they refused to let me speak to one. Now I am sitting here with this matter unresolved and I don’t know what my options are to resolve the matter.