Donated $5 to make a wish in front of place. Got a...

Donated $5 to make a wish in front of place. Got a promo card for free $20 power card when you purchase a $20 card. Went to cashier and asked for the 20/20 deal and gave card. I was charged $26 because the employee told me D&B upcharges the $6...that there is no $20 card when super charging. I said ive had coupons before and paid 20 and got 20...in fact had rhe offee that day on the app that i used! Rhey said "thats just the way it is... and how they make ...money!" I was DUMBFOUNDED! I work in retail and would never explain something to a customer that way...telling me D&B is stealing $6 bucks from me....meanwhile I gave the $5 to charity plus an up charge of $6....didnt save much! Will only stick to app purchases now since in store likes to con customers!