If Found, Return to Hell - Em X. Liu

"Welcome to One Wizard! How may I help you?"
Being an intern at a wizarding firm sounds magical on the page, but in practice mostly means getting yelled at by senior mages—and angry clients who've been turned into platypuses. So when Journeyman Wen receives a frantic call from a young man who's awoken to a talisman on his bedroom wall and no memory of how it got there, they jump at the chance to escape call center duty and actually help someone for once.
But the case ends up being more complicated than Wen could ever have anticipated. Their client has been possessed by a demon prince from Hell, and he's not interested in leaving.