Another reason why the only airline I will ever fly in the United States is American Airlines. They have, from my experience, the best customer service. I've never lost a bag, never been charged fees that weren't up front, and I have never had a problem with their representatives.
American Airlines will actually take previous checked baggage tags off my suitcase(s) if there are any before putting the new one on. They also don't charge me for my baggage because I hand them my military I.D and that waives all the baggage fees.
They even once waived a ticket change fee because my schedule had changed and I only paid the difference in the airfare, instead of the $150 change fee.
Also, don't get me started on FedEx. They are worthless! I only ship items through UPS if I can avoid FedEx at all costs.