They do that all the time man.
I recently thought I had to resort to them 2 weekends ago.
A friend of mine threw a birthday party for his son. The kid wanted WWE2K17 for 360. Bestbuy didnt carry it so I went to 2 different gamestops that showed they had the game in stock through the website.
Each store I went to they had the game open but were trying to sell the game as new.
The first gamestop I went to I asked the employee "If I bring a brand new game in here right now, still in the wrapper, and I open it up right in front of you and say I want to return it for my money back would you let me?"
"Well, we could let you exchange it for another copy of the same game if there was something wrong with it, or give you a store credit".
"Right. So you wouldn't give me my money back because as soon as I opened it you would consider the game used" and I bounced.
Went to the second one and they hit me with the same story except this employee was a bit more aggressive and smug.
"Well if you're worried about it being wrapped in plastic I can put it in a plastic sleeve for you and you wont be able to tell the difference."
"Really. Let me stop you right there. This is exactly why Gamestop is going out of business. Why would I pay you full price for a game you already opened when i can go to the walmart in this same exact shopping center and get the game unopened for the same price?"