Unfair hand over to Attorneys

MTN decided to hand my account to attorneys without my knowledge. MTN stopped debiting my account of which I wasn't aware. I took out a contract with them and gave them my account details to debit on my payday. All of a sudden today I got to know that they stopped and are now blaming me for their mistake of not debiting my account. All my debits are paid and the date that was given to MTN there is always money in my account. Not at once am seeing any missed debit order from MTN nor was I ever called by anyone from MTN around this matter up until now upon receiving a text message from HP Attorneys. I have never in my life failed to honour my debits nor was I ever handed over to any attorneys for non-payments. MTN must please rectify this and reinstate my debit order as previously agreed. I am not willing to pay R7390 that am not aware how it occurred?