fixer vs service man

fixer and service man both are nouns.

Word	Noun	Adjective	Verb	Adverb
fixer	Yes	No	No	No
service man	Yes	No	No	No

As nouns, service man is a hyponym of fixer; that is, service man is a word with a more specific, narrower meaning than fixer:

Other hyponyms of fixer include darner, maintenance man, repairman.

fixer (noun)	service man (noun)
synthetic narcotic drug similar to morphine but less habit-forming; used in narcotic detoxification and maintenance of heroin addiction	a skilled worker whose job is to repair things
someone who intervenes with authorities for a person in trouble (usually using underhand or illegal methods for a fee)
a skilled worker who mends or repairs things
a chemical compound that sets or fixes something (as a dye or a photographic image)