call back vs call in

call back and call in both are verbs.

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

As verbs, call back and call in are synonyms defined as:

Other synonyms of call back include recall, withdraw.

call back (verb)	call in (verb)
recall knowledge from memory; have a recollection	make a phone call
summon to return	summon to a particular activity or employment
return or repeat a telephone call	summon to enter
cause to be returned	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