telephone service vs telephone company

telephone service and telephone company both are nouns.

Word	Noun	Adjective	Verb	Adverb
telephone service	Yes	No	No	No
telephone company	Yes	No	No	No

As nouns, telephone service and telephone company are synonyms defined as:

telephone service and telephone company: a public utility that provides telephone service

Other synonyms of telephone service include phone company, phone service, telco.

telephone service (noun)	telephone company (noun)
a public utility that provides telephone service	a public utility that provides telephone service