incorrect date billing

i had an agreement with Mondo to run my debits on the 25th of every month(cell phone contract).To my surprise i just received an sms starting that my account is in arrears of R379.67. I called Mondo and they advised that i must speak to Telkom.I called Telkom and the lady told me that i signed for my debit order to be ran on the last day of the month.I called Mondo again spoke to Nicole Nair and she confirmed and send me a screenshot of which states that my debit should run on the 25th of every month.My question is.

1.Now because there is no funds in my account my line will be suspended for the mistake i did not commit After all i tried to make an arrangements to pay the total amount on the 15th december and none of the cunsultants agreed - -still my line will be suspended for the mistake i did not commit.