Unable to pay credit card

I do all my primary banking with FNB. The app works well, as well as internet banking. Recently I obtained a Nedbank Credit Card. Now I'm trying to pay this account online (internet and the fnb app) it says 'invalid account details' yet all the details entered are as per my bank statement. I spent 2 hours between the Nedbank Branch and FNB branch in Sandton City. All they could advise me is that I must withdraw cash and go to an atm and do a cash deposit. I rarely ever transact in cash because the app and internet banking is so much easier. So now each time I need to pay the credit card I must go to an atm. This is such an inconvenience. Also, my address is incorrect on both my FNB and Nedbank accounts. Yet I submitted my proof of residence so many times I can't count. I'm slowly losing hope in both Nedbank and FNB.