service fee vs service charge

service fee and service charge both are nouns.

Word	Noun	Adjective	Verb	Adverb
service fee	Yes	No	No	No
service charge	Yes	No	No	No

As nouns, service fee and service charge are synonyms defined as:

service fee and service charge: a percentage of a bill (as at a hotel or restaurant) added in payment for service

service fee (noun)	service charge (noun)
a percentage of a bill (as at a hotel or restaurant) added in payment for service	a percentage of a bill (as at a hotel or restaurant) added in payment for service
	a charge paid to the owner of an apartment building for electricity, lifts, maintenance, etc.