Money reserved from my account

It's the second time now I am writing with the same complaint.Last time I wrote,fnb even responded here and said they would call me within 48 hours.Its been 3 weeks now and I am still waiting.I dont know why the only one bank I have had in South Africa has decided to make me miserable like this.R5000 was reserved from my account because they said they are investigating a ***** case,which I am not aware of.May i please be contacted and be made aware of what is happening.Please how can I be at standstill because my bank has withheld my hard earned money without even giving me prior notice.I am so disheartened.