Mtn is *****ing money

I took out a month to month wifi contract and paid 1month in advanved. They cut off my internet the middle of a month that I fully paid for because the next months debit order didn't go off. So I paid for the next month, internet was back on. Requested a different date for the debit order to go off, that was apparently changed but still went off on the same date. Now my internet was cut off on the 8 of January (which was paid for). How can you cut off a month to month service in the middle of the month that was paid??!!!!!!!