Try repeatedly entering and exiting their area. Check periodically to see if they're offering a battle. Trainer's in my game rarely call to offer a battle, and never offer a battle if I try and call them.
Inside every older person is a younger person wondering, "What the hell happened?"
No check your Match Call in the PokéNav, it will show a Square "Pokéball Symbol" next to the name if they want to battle you.
For normal Match Call Trainers it randomly checks to see if they want a battle with you everytime you enter the route they are on.
Gym Leaders, is not quite the same, Some people claim if you keep entering and exiting their town a Gym Leader will rebattle you, I have a different theory and have not proven this yet, but I believe they work on a step system for checking rebattles, Similar to how egg production works. When I get rebattles with gym leaders a lot of times I have not step foot in their town in weeks.