re: Do's and Dont's of customer service...

The customer is always right, but right or wrong your goal is to help them whatever that takes.
Always be polite, even if they aren't.
Never raise your voice to a customer.
Always offer to find a solution for them.
If you can't please them in any way, offer their money back if that is possible and wish them well.
Use the mute button on your phone to yell at the wall, not the customer.