I took on my dog from a rescue place as a 2 year old. He was pretty much completely untrained.I got him to sit , stay etc.the recall i did by using a long rope,whistling him back & giving him a bit of meat. after a couple of months i could whistle him back even when i'd lost sight of him,however sometimes now when recall him he'll look up at me then carry on scenting around and ignore me. i know he's heard me and he knows what the whistle means,so why doesn't the f***er come back.he always returns to hand when on the lamp & is obediant apart from this fault.how can i get him back EVER