FNB is unable to account for the missing funds in my credit card.

I've contacted FNB numerous times regarding the missing money in my credit card. I've requested a detailed statement including all the balances and they have failed to do so. Their credit card statements on the FNB app does not contain balances, when I call the credit card department no one is able to give me answers. I was advised to send an email to ***, I received an email stating that they are attending to my request, I'm still waiting. I sent a follow up email, I didn't get a response. They can't tell me how much my balance was before I increased my limit. There are funds that are not reflecting and no one is able to account for this. Now I'm stuck with a balance that makes no idea and because of this, I've decided not to use my credit card which is an inconvenience and defeats the whole purpose of having a credit card. This is frustrating to say the least.