Doing someone a favor can make you like them more, not the other way around

Benjamin Franklin wrote that he won over a rival legislator not with flattery but by asking to borrow a rare book from him, a favor that seemed to warm the man toward Franklin rather than the reverse. A 1969 experiment by Jon Jecker and David Landy found the same pattern: people induced to do someone an unpaid favor rated that person as more likeable afterward.

— Jon Jecker, David Landy, Liking a Person as a Function of Doing Him a Favour — Human Relations, 1969