call centre vs call center

call centre and call center both are nouns.

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

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

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

call centre (noun)	call center (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)