cable television service vs cable television

cable television service and cable television both are nouns.

Word	Noun	Adjective	Verb	Adverb
cable television service	Yes	No	No	No
cable television	Yes	No	No	No

As nouns, cable television service and cable television are synonyms defined as:

cable television service and cable television: a television system that transmits over cables

Other synonyms of cable television service include cable, cable system.

cable television service (noun)	cable television (noun)
a television system that transmits over cables	a television system that transmits over cables
	television that is transmitted over cable directly to the receiver