telco vs phone service

telco and phone service both are nouns.

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

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

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

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

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