Try putting one finger gently against his bowl and rub in small slow circles to get his attention. I have taught many bettas to come when called this way, and it can soon turn into a game of tag!
Bettas are highly social fish, if you don't play with them they get just as bored as you do! When you feed, try 1 pellet at a time, and each time slowly move your hand closer and closer to the surface of the water. Eventually he will learn to come take the food right from your hand.
In starting that way, I have taught many bettas to "play" with me... the possibilities are endless and will be determined by the personality of your individual fish.
And, talk to him!!!! My bettas always respond when I talk to them! They can't hear you the way people hear each other, but there are vibrations from your voice, and they learn to distinguish that from other vibrations!
Good Luck and have fun!