If the pup is only 4 months old I would suggest a harsh voice and running him down. I am a member of the FGOFS (Fat Guy Old Fart Society) but this is what I do. My son is training his 1st dog, a GSP. My son bought him when he was three months old. The dog is 4 months old now and the 1st time I told him to come after demonstrating he knew what it meant, he ran the other way. I huffed and puffed after him and caught him and explained to him I wasn't happy with his behaviour. I wasn't harsh but I was firm. A pup of this age is like a 7-8 yo human. They can handle harsherdiscipline than a 2yo but not like an adult. Chase him down and have a "Come to Jesus" meeting with him and you'll have a proper acting dog.

Dr Fatguy