Debit order bounced due to delayed transaction registration and fees charged

I paid my credit card installment on Sa****ay the 30th of April 2016, effectively nullifying my automatic installment. Enough money was left in my cheque account to honour my remaining debit orders. Due to it being a long weekend, FNB did not register my payment into my credit card until Tuesday 3rd May 2016, even tho the money reflected in the credit card and i was able to spend some of it. FNB then proceeded to debit the minimum payment due (which should have been R0.00 after my payment), a sum of R750.00, causing my remaining debit order to bounce, costing me a R100 fee. THEN they bounced their own minimum payment debit order too, resulting in another R100 fee. After calling the help centre, I was told there was nothing they could do, because my statement says it happened on the 3rd of May. I find this a disgusting and seriously antiquated banking practice for a "so called" forward thinking bank such as FNB. I feel FNB should refund my R200 in ridiculous banking charges and admit it is an irregularity in their system that caused this error and not my fault.