Q. How can I locate the actual phone number of a US Post Office (not the generic 800 number)?
There is an official site called uspassporthelpguide.com; but a quickest way to gain information within this online database is to perform a Google search. Enter (for example) Tucker Georgia Post Office passport.
When you arrive at the resulting uspassporthelpguide page, the actual local phone number for the actual post office is listed.