FNB took money from my account without a mandate

Hi

I have a personal loan account with FNB and I have been in arrears with them due to the fact that I was under debt review, I'm not under debt review anymore and i made arrangement to pay an amount of R1870 for the next 6 months, FNB took the aforesaid amount and send message confirming that money went towards my loan account. Today I received a SMS from FNB saying they took off a R5000 from my account due to arrears. Bear in mind I still have a bond that needs to go off.

So what was the use of making a arrangement which I kept and FNB decided to take of an additional R5000 just like that. FNB is a dishonest institution and I've been on the phone for almost 2 hours due to them putting me through from one dept to another, finally while I was still on hold computer generated message say please note our office s are now closed.

FNB would you rather prefer me closing my account with you and pay you like R100 a month where I know you can't put your sticky fingers in and not take which was not prior arranged? PS, may I add this is not the first time this happened.

Hello Peter please assist.

Thank you

Mureeda