Surprise R6152 Debit off my account

I would love nothing better than to praise the bank i choose to bank with, but today i have a heavy heart and am filled with stress!! FNB debited my cheque account for R6152,98. After an hour on the phone and getting confused responses as well as going from department to department i felt i would have a better result going into the branch at Cresta. Another hour in the queue and another hour of the clerks trying to get to the same department which was the Legal department, i was told that they needed to check with the Admin department because they cannot see where the payment is and also that the reference wasn't matching to a credit card because it wasn't 16 digits. So what must i do now??? I pay my credit card accounts every month, there was no communication that this was going to happen or query if i could afford this. Its January FNB!!!!! I am a single parent, i support 5 other people and cannot afford such a setback. I haven't even paid my rent yet, let alone school fees etc. I need this money back into my account immediately please.