Post-Office box vs call box

Post-Office box and call box both are nouns.

Word	Noun	Adjective	Verb	Adverb
Post-Office box	Yes	No	No	No
call box	Yes	No	No	No

As nouns, Post-Office box and call box are synonyms defined as:

Post-Office box and call box: a numbered compartment in a post office where mail is put to be called for

Other synonyms of Post-Office box include letter box, PO Box, POB.

Post-Office box (noun)	call box (noun)
a numbered compartment in a post office where mail is put to be called for	booth for using a telephone
	a numbered compartment in a post office where mail is put to be called for