R500 Overdraft declined- ENOUGH WITH FNB

I am enough with FNB and i regret leaving Nedbank. Firstly, my salary is been going into this bank every month since March 2014. I also have a 32 day Interest plus account with FNB and i have enough money in this account to cover any unforeseen circumstances. Now, i app**** for a mere R500 (FIVE HUNDERED) overdraft on my cheque account and it was declined and i was not given the reason....is this how this bank is treating customers? I really regret leaving NedBank. I can see that FNB is never ever going to help me with anything nor matter how loyal i may be to them. I am disgusted.