Amazon.com is a rare bastion of remarkably great customer service in a marketplace devoid of such due to the effects of cost-cutting to keep prices low. Amazon.com seems to use a good bit of its cost-advantage stemming from the fact that they're both huge and have no B&M presence to provide this superior service.
Do be aware, though, that Amazon.com sells things, but
also other companies sell things through
Amazon.com. Even within that second category, there are two different approaches: Companies that use Amazon.com just for the sales and money side of things, and companies that also have Amazon.com "fulfill" the order (i.e., ship it). However, in either case, the customer service provided, especially as it pertains to returns and such, are the policies of the actual seller, not Amazon.com. Amazon.com only provides customer service for things you actually purchase from them; if you buy something from someone else, on their website, then your recourse, should something go wrong, is with the actual seller. In a way, Amazon.com is both a store
and a mall that contains other stores.