My wife works at the customer service desk at the front. You wouldn't believe the shit she puts up with from customers. She's had people try to return shit 5 yrs old, saying they bought it last week. She's had people throw crap at her, swear at her, and generally be rude. If you come to the desk acting like a dick, you'll get treated as you deserve.
Sure, it's a big chain store, so they have their policies. Some of the department staff are good, some aren't. Don't like it, too bad.. shop somewhere else.. Remember, they want you coming back and spending money, so if they can make you happy, great.
That being said, if you truly have a problem, and need something that the customer service desk can help you with, ask nicely and cut them some slack. People are quick to be rude to retail workers when they don't get their way. Remember, that's somebody's mom, dad, sis, brother, etc.