unplanned debt

<p>I have a business account with std bank for quite sometime now, the problem that I have write now is really painfull and it is happening for the second time. I was expecting money from different people and the whole last years December I did not use my account since I hired a car with Avis so biggining of this year I saw money in my account and used it because i was expecting money from my clients and now I have R6000 that I must pay to std bank and I dont know what is it for. this is happening for the second time and this time I want to know why am I liable for their mistakes if it is a mistake and why do they put money in my account and put pressure afterward threatening to put charges as if I app**** for credit with them? I want answers .</p>