Worse customer service and bad service all round

So i have a credit card with fnb of which the payments get debited monthly. Ive never missed a payment and for some reason ive been told that i have not paid thr full amount. I do not understand hoe this can be when fnb debits my account and there was never a time when there were funds short. I am so ****ed because when i called to have it sorted i was on the call for almost an hour and I didn't get to speak to anyone. I then decided to request a call back only to be on hold for 10 minutes with the consultant and the ca to be dropped. My issue is still not resolved and this situation is affecting my credit score.