Systems off on Sunday's and Public Holidays

I have a credit card with Nedbank which was over limit and I knew about it. When I made a payment to my credit card from my Nedbank cheque acc on 26 April 2015. On the 28th the payment did not reflect on my credit card. I phoned the credit card department and was forwarded to collections seeing that my credit card is over limit. I wanted to know why my payment has not reflected seeing that the that it was done from another Nedbank acc. The answer I received was that the Nedbank services is not available on Sunday's and Public holiday's. I asked if the servers is switched off on these days and the answer was yes. I was then advised that the payment will be processed at the end of the first working day. This for me is ridiculous and I don't know why I am with a bank that takes 3 days to process inter account transfers or who switch off servers on Sunday's and Public holidays.