phone company vs telco

phone company and telco both are nouns.

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

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

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

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

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