Complimentary is correct.

"Complementary" (with an e) means enhancing or harmonizing. e.g. "Her vocabulary complemented her charm."

"Complimentary" (with an i) means either "expressing praise" or "offered free of charge"

e.g. "The Medium commenter offered complimentary grammar advice"

https://www.thoughtco.com/complementary-and-complimentary-1689348