Very Very Disappointing in First National Bank

Nothing could explain how disappointed I am in First National Bank. The bank which I chose above all banks. a Bank that gives you the personal sense that they do care. I am a Gold Credit card holder that upgraded in the beginning of December 2019 to a Premier Card. I currently had a 19800-credit limit and they add a 19800 on the Premier credit card also. I start using the funds during this couple of days which I knew that my salary will cover the instalment. All together a minimum instalment of R1350 would have been for this month …I guess. I immediately forward my salary to my credit card on 20th December 2019 not nothing that a R6100 will be deducted from my money which is the amount I used on the Premier cc. I contacted FNB and everyone gave a different story until I went in the bank today. They told me that I went over the limit and that is why the bank took that amount which I used from the Premier credit. My question to the consultant was "Why did nobody contacted me to explain that such amount will be deducted or why did they not make an arrangement with me. I was quite emotional for the fact that any arrangement could have help, but they did not care. The system did not allow it was their words which I do not believe. I never missed instalments and is a loyal banker why could they not made arrangements? It is the end of year and now I am R6100 short which could have been prevented. I did not expect this from FNB and funny enough I did have a feeling this morning that I do not have to stress, because they will make arrangements with me, but nothing was done. They asked me if I would like to have a limit increase on my Premier account and obviously it declined, due to the system. I am so unhappy and speechless.