Mr kammies

I would just like to know it's not the first time I have noticed this, I expect this from Rcs but I have bought on my account it shows how much credit we have left afterwards, but when got to a shop knowing my account balance it was less than what the slip shows I have left, this leaves a person fuming, I mean monthly you get paid on time, why is my credit getting less if you are paid on time, and every month the due balance are paid , I have no magazines or anything added this is a ******* I didn't have this problems before I always had the benefit of using what my credit showed, now it's we pay and your credit gets less aswell what charges it's taken for I really would like to know, because I pay my account every month on the 25th so what is extra being chargef dusting the month after it has been paid