MTN - How many hoops do I need to jump through to change Debit Order details?

I have tried since the beginning of the end of April to have the debit order on my MTN contract changed from FNB to STD Bank. I do not get any responses, and when I do it is a form for me to complete - just to change a debit order. When I responded to that request and mentioned I do not have access to a printer, and can I just send confirmation letter from the bank with my details on, I did not receive a response. That was 22 May. Since then two debit orders have been presented to my bank, both were rejected and cost me R110 each time for bank charges. This is absolutely ridiculous!! I have even tried to call MTN and all I get are robotic options that do not meet my query. I bet that MTN will be quick to cut my service for non payment. Please CANCEL my debit order, as this seems to be beyond MTN's capabilities to change debit order account details via email (in these times when so many people are working remotely), and I will rather pay my account every month manually.