call center vs call centre

call center and call centre both are nouns.

Word	Noun	Adjective	Verb	Adverb
call center	Yes	No	No	No
call centre	Yes	No	No	No

As nouns, call center and call centre are synonyms defined as:

call center and call centre: a center equipped to handle a large volume of telephone calls (especially for taking orders or serving customers)

call center (noun)	call centre (noun)
a center equipped to handle a large volume of telephone calls (especially for taking orders or serving customers)	a center equipped to handle a large volume of telephone calls (especially for taking orders or serving customers)