Unfair charges on a cheque account that allows for negative amounts

I got charged R180.00 for #Item Paid No Funds 1 yesterday, then today R225.00 #Item Paid No Funds 3.

I am using a cheque account that allows to go to negative, I do not understand why am I charged such a ridiculous amount of R405 when my cheque account allows for a negative amount.

Can you please fix your system please.