telephony vs call in

telephony is a noun but call in is not a noun.

Word	Noun	Adjective	Verb	Adverb
telephony	Yes	No	No	No
call in	No	No	Yes	No

telephony (noun)	call in (noun)
transmitting speech at a distance

telephony (verb)	call in (verb)
	make a phone call
	summon to a particular activity or employment
	summon to enter
	cause to be returned
	demand payment of (a loan)
	pay a brief visit
	take a player out of a game in order to exchange for another player