Need Affordable Book Cover Design Agency.

We are a group of University friends and we had to get together last night we discussed many topics, and one of my friends revealed that he is an author and writing his first book, we were curious about his journey but he said that he is facing some issues with book cover design and not getting any solution then I decided to help him out, so I am searching for the book cover design services, can anyone recommend agency like professional book cover design service or any other?