Bought a $25 itunes gift card from 7-11 and it was invalid, cashier was too busy on the phone with a personal friend and didn't give me a receipt, please help!

I bought a $25 iTunes gift card from the 7-11 in Windsor Locks, CT earlier this afternoon around 6:45 P.M, and when I tried to activate it, the code was invalid, and when I called the 7-11 to let them know what happened, the foreign man that answered the phone started yelling at me when I told him the cashier was the too busy on the phone with a friend to give me a receipt for my purchases. Considering that my card didn't work and the guy yelled at me when I was trying to make him aware of the situation, it made me wonder how many other people has that convenience store scammed into buying invalid gift cards? If they are scamming people, is there a way for me to report the store to Apple for using the company to gain fraudulent dollars? Is there a way I can get my money back?