Nedbank Over charging me for nothing

I have a problem with Nedbank been taking my money as an overdraft that I have never even had, first incident had a minus of R600 something and they told me that the money was not going out for the transaction I was making since it was the weekend does that even make sense, second incident yesterday paid my rent around 8 of R6300 money when I woke up they’re 2 transactions on the same amount and I only had R6348 in my account, how come I had 2 transactions of this amount when I only had R6348, now my account is on the negative balance of R6254, for what the person was sending to only got ar6300, and I was using payshap , I’m sick and tired of Nedbank overcharging me for nothing I want my money I want to close this bank, and people should stop using such bank