I visit my local GameStop once a week, have become friends with the workers there, and we sometimes talk for an hour about the company. They say how their store is often stolen from, how the shipping companies sometimes don't pick up packages, higher-ups make bad decisions that customers hate and take their anger out on them. My point is these employees are underpaid, understaffed, work too many hours, and have to deal with so much crap from decisions that are beyond their own. Cut them some slack and be friendly to them, if you are they try to help you out the best they can.
Also, this is from both personal experience and recommendations. Never buy anything online, customer service sucks, and clearance items cannot be returned, so take a good look before purchasing. If you want to buy POP Figures, understand the longer they are in the stores the more damaged they may be/have stickers on them. If you buy the last copy of a NEW game, the case is out on display so they can have a live update to the customers on whether they have the game or not, the game is never played or used, just "gutted" to have a display case (they need to put a clear seal sticker on the "gutted" case when sold). If you complain about a preowned game case being damaged or replaced with the GameStop generic cover art, understand that it was previously owned, so that's why the case my be damaged, or the game was brought in with a lack of a case so they had to create one. Last thing, please make friends with the employees, the nicer you are to them the more they will try to help you, even will give you some of the posters from around the store when taken down.