Back when I was a manager of a Gamestop, I had to say something to guys coming into the store like that from time to time. I'd start out with something fairly polite, but obviously aimed at their behavior and not a general rule. Something like, "I think it's time for you leave."
Of course, the guys were obviously socially oblivious (hence the situation in the first place), and eventually I'd need to step it up. Unfortunately, due to the rules about how employees are supposed to treat customers, there wasn't much the girls working there could do for themselves. IDK if that's still the case, but it sounds like it.
Granted, I - myself - broke the rules when it came to selling games. This actually resulted in a hilarious meeting with our district manager. She started off with something like, "We've been going over the numbers, and you have the highest sales in your store by far. I've been sent to talk with you about what you're doing, so we can make improvements." So, I said something like, "Oh, I don't really have a technique. But I play a ton of games, so I make sure to tell my customers which ones are good and bad. A huge majority of our business relies on repeat customers, so they know they can trust me, either because they loved my recommendations, or because they ended up not liking a game I told them wasn't any good. So now, when they come into the store, they'll buy a game they've never heard of it I tell them it's great. In fact, I can barely keep Half-Life stocked."
She started to get angry and said something like, "You can't do that!!" "Do what?" "You can't tell a customer a game is bad! We have deals with these companies!" "So...you want me to stop doing the thing that's boosting my sales...the whole reason you're here?" "Yes, you have to."
I didn't.