telephone company vs telco

telephone company and telco both are nouns.

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

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

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

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

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