I had the same problem with Tino when he was younger. I would call and call and call and he would never come. Yorkies are stubborn! However they are also very clingy so I used that to my advantage. If Tino would not come when called within 3 times of asking for him to come to me I would say "Fine, I am leaving you" (as if I were going to work or something) and I would leave the situation, whether outside or inside (don't walk to far but don't look back) It works like a charm every time, he comes bounding toward me and I commend him for being "such a good boy". Ever since that he has never hesitated when called. With the exception of when he is sleeping in the bed and he knows mommy really does need to go to work, then he is just being lazy and doesnt want to get up LOL!
