FNB debit orders on my overdraft

Hi FNB

You guys ran a debit order earlier than our agreement, and went through my overdraft account, I do not like this as this means I going to be paying double the interest, the overdraft interest as well as my normal loan, this is a ****, please advise how you going to fix this? I phoned the the call centre, I was transferred from one call centre to the next, they don't know how to help resolve this issue, my last reference was " FNB :-) Your Call Reference number is Rk ********** 3284." both my Loan debit order and my revolving loan debited earlier than they supposed too, it very unfair that I should pay for that overdraft interest. Looking forward to your feedback.