service charge vs service fee

service charge and service fee both are nouns.

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

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

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

service charge (noun)	service fee (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.