The thing is... customers now just assume everything should go their way. I used to be a manager in retail, and my new saying is "A person can be smart, but PEOPLE are STUPID!!!"
Seriously though... If the reciept, signs at the cash register, and the sign on the door ALL say "New merchandise may be returned UNOPENED for cash back or store credit. Defective OPENED merchandise may only be exchanged for the same item." (I worked in a movie/music store. It's a copyright LAW that we can't take back an open movie/CD because it's the 'wrong one'... people will take them home, make copies, then try to return the original and get their money back... Not everyone, but the dishonest few have ruined it for everyone) yet customers would come in and get PISSED when we refused to trade one movie for a different one... Is the customer right? HECK NO! They should READ the policies before expecting us to break them.
If the customer is respectful and polite to me, I would always go the extra mile trying to help them out, even if it meant bending (NOT breaking) policy a little. BUT if a customer is a jerk, then I am going to stick to policy exactly. (While being extremely polite and courteous. lol.)
Also... make sure you do actually LISTEN to the customer. I have intervened when an employee was sticking to their guns, and the customer was pretty irate, only to find out that the employee would jump to their own conclusion about what the customer wanted. The customer really WAS in the right... so make sure that you KNOW for sure what the customer wants. (the employee thought she wanted to exchange a brand new CD because she accidentally dropped it on the gravel outside when she opened it... all she wanted was for us to run it through our resurfacing machine, which was no problem...)