First National Bank
Incidental credit fee R57... please explain this

I would just like to know, whats the criteria used to charging the R57 incidental credit fee?
I get billed every single month for the R57 over and above the R100 that I pay for my account month on month.
Please help me, I just want to know why that amount was charged?
I also have value added services that range from R22 one month to R120 the next