Wrongly penalized for other's mistakes.

It might be a little late for this,but I have noticed that on the 29/11/19,I was charged "Declined Authorisation" fee,twice,despite the fact that there were more than sufficient funds available in my Credit Card Acc. at the time (& I can prove it). Now,whether the fault was on the side of FNB or the vendor (Checkers Hyper,Arcon Park,Vereeniging),it sure as hell was NOT mine. In this day & age,R17 is not going to make a whole hell of a lot of difference to me,but it's the principal of the matter. Why must I be penalized for other's mistakes?? Besides which,I am so FED-UP with way in which FNB has been treating me. Also during the latter part of last year,they started charging me with interest that they insist was for an "interest bearing transaction",despite the fact that there were absolutely NO BUDGET TRANSACTIONS on my Acc. whatsoever. After an INCREDIBLE AMOUNT OF WASTED TIME (& money) on the phone & finally having to go to a branch,the replies that I received were just ABSOLUTELY RIDICULOUS & PATHETIC! Basically,I was told that they could not even tell me for how much longer I would be charged those interest fees,nor could anyone even calculate how much the interest fees amounts would be. Is that an answer anybody is seriously supposed to accept from an "Authorized Financial Services Provider"??? It is absolutely laughable,if it hadn't cost me money. Then,just as suddenly as they started,the interest fees stopped being charged. As far as I am concerned,not only does FNB owe me a refund for the "Declined Authorisation" fees,but for every cent of those interest fees,which NO ONE AT FNB could explain,& still can't,to this day. If I can get a Credit Card from another bank,with the same,or greater credit limit,I will be dropping FNB like a bad habit.