Massive debit order mistake and I now can't get hold of anyone to fix it.

Very frustrated at the moment. I have recently immigrated from South Africa to Europe, but want to still keep my South African number. An upgrade of my contract was necessary as it had expired, so I attempted to move to the lowest cost package that I was able to at apparently R209. The debit order request has now come in at R20,000. I have tried to phone MTN to fix this mistake, but when attempting to navigate the telephonic menu, it says that my phone number is invalid and I can't proceed. I'm not going to approve the incorrect debit order, but I'm also worried that my number will be canceled if the debit order doesn't get approved. Please MTN, help me help you.