I would invest in a dog whistle. Some dogs get really preoccupied with so much going on and drown out other noises, even your voice. Another thing is, have you ever punished him for not coming to you? That is a big mistake people make. They do it out of frustration. But the dogs remembers it and then is like, 'no way I'm going to you, I might get hit'. Or even if you start to act angry that they're not coming. They pick up on that kinds of stuff. I would use positive reinforcement. Invest in some tasty treats. I like puperoni. You can break off pieces. Or cheese. Call the dog and hold out the treat. When he comes, praise like crazy and give the treat. Repeat this anytime you call him. Always give him a treat when he comes over. After a few weeks, he will think that coming means good things, or at least praises and lots of pets and will start to come more.