Expired can of Monster Energy Ultra

Today, I picked up 2 Mega Monster Sugarless cans from the Monster fridge right next to the cashier as I normally would. I got home and cracked one open and it was flat, no carbonation whatsoever...it was strange, I opened the other and it was fine. Then I decided to look beneath the can for the "BEST BEFORE" date. You packed and sold a can that expired in June. I would expect for a reputable retailer such as yourselves you'd take inventory of bad products, but I was wrong...I even drank from the can before I checked it's shelf life. This is a health hazard! I've kept my till slip and took pictures of the can for evidence. I'm irritated by this and expect a full replacement.