armed services vs call up

armed services and call up both are nouns.

Word	Noun	Adjective	Verb	Adverb
armed services	Yes	No	No	No
call up	Yes	No	Yes	No

armed services (noun)	call up (noun)
the military forces of a nation	an order to report for military duty

armed services (verb)	call up (verb)
	recall knowledge from memory; have a recollection
	get or try to get into communication (with someone) by telephone
	bring forward for consideration
	call to arms; of military personnel
	cause to become available for use, either literally or figuratively