My question involves name change laws in the State of: Georgia

My son is 3 years old and his father hasn't really done anything for him since he was 5 months. We stay in the same city almost but never see eachother. When ever he does call to see my son, he doesnt come pick him up. His mother and sister keep him for me sometimes but he doesn't do anything. He does not keep him, and he doesn't provide for him in anyway. His name is on the birth certificate but he hasn't had him legitimized. I also started a child support case against him and he never went to the office to talk to the people because he said he wasn't going to pay. His dad says he doesn't care if I get his name changed but he won't sign over his rights. Is there anyway I can change my son's last name without his consent? or even I have to have his consent, what do I have to do to get started with the process.