What's happening FNB?

I contacted FNB via the app for the regarding the available balance on my credit card. My query is quite serious in where for 3 days in a row the available balance on my credit card has dropped without me using it and without any new transactions popping up. The same happened earlier in the month but corrected itself a few days later. I need an investigation reported for this and am not being told your systems are down and I should contact you at a later stage by your consultants. This feels like you're just passing the buck. Why not offer to call me back when your systems are up?