telephone bill vs phone bill

telephone bill and phone bill both are nouns.

Word	Noun	Adjective	Verb	Adverb
telephone bill	Yes	No	No	No
phone bill	Yes	No	No	No

As nouns, telephone bill and phone bill are synonyms defined as:

telephone bill and phone bill: statement of charges for telephone service

telephone bill (noun)	phone bill (noun)
statement of charges for telephone service	statement of charges for telephone service