We get dozens of emails each week asking if we know the toll free 1-800 phone for Amazon and for FBA (the Amazon warehouse, otherwise known as fulfillment by Amazon). The bad news is, there is no phone number for FBA. Sellers are out of luck - the only way to contact them is to start a support ticket.
The good news is, if you're an Amazon customer, you can contact Amazon 3 ways - by email, by "click to call" (log into "My Account" and find the link), or by calling this toll free number (a 1-866 number, not a 1-800 number, but it's still free):
1-866-216-1072 (US only)
1-206-266-2992 (international customers)
Good luck!