telephone service vs telco

telephone service and telco both are nouns.

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

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

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

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

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