****med of my money at fnb

I have been de*****ed of my hard earned money which is under the care of first national bank.This guy called as if he was from fnb,and before I new it R6000 was gone from my account.I reported the matter to the bank and they promised to contact me within 24_48hrs,this happened on Tuesday the 24th and up till now I haven't heard from them. Their service is very poor and don't care. I entrusted my money to them and expect it to be safe with them therefore I want them to re embers me.As a bank they need to ensure that my money is safe and ********* do not just access our accounts as easy as this.within 30 minutes 6000 was gone,and it was 1000,a 1000, 1000,1000 until it was 6000,why didn't they suspect ,it was not like 6000 at once.