Ours is stubborn, too! He is 10 months old. If he just stares at me without coming when called, I turn my back and wait or run away like something is interesting elsewhere. Eventually, curiosity will get the better of him and he will come and see what I am up to. Then I give him lots of praise and a treat (I hide the treats as I don't like to bribe, only reward). He now comes when called because we did this so many times.