Bad service

Yesterday I received a call from FNB agent and she said I qualify for for a credit card limit increase, the amount was a lot and I informed her I don't need that much money I can only increase the limit by R1000 for some reason she said the app doesn't allow R1000 it only allowed R900 increase which I agreed to and she said they wont be any initiating fees, a few hours later when I log on to the banking app I see there is R511 on my credit card it's not the R900 that we agreed on. I have been on the call with FNB for over an hour to find out what happened, I have been transferred from pillar to post without any joy.nobody knows what has happened. I was trying to find out how much was put in the credit card and if they put R511 they must reverse that money I don't want it because that is not what we agreed to