For the most part, in retail, you get the customer service that you pay for.
Higher end clothing stores, or at least trendy ones, usually have good customer service, whereas at places like Walmart, the clerks probably do not care. They aren't paid enough.
From what I have seen, it is quite the opposite; Dillards has the snottiest workers, while JCPenney is friendly. The same for Wal-Mart. I believe Wal-Mart has a courtesy policy. Then again, I live in a part of the South where many people think wearing Tommy Hilfiger everything constitutes some sort of godhood.