mtn failed to debit their money and listed me as a defaulter yet they are at fault

i have a new contact with mtn and they only debited i think twice and all other months they didn’t . i couldn’t make payments myself and now i am listed on itc for something that isn’t my fault. i signed a contract agreeing to a debit order and mtn failed to honor the agreement. i have my bank statements to proof i had money on those debit order days. it’s unfair i am on itc in this regard