Yardwood

Hi, ive got a beautiful 4 year old dog that has been so gentle to all people and other dogs all his life. Since he got attached six months ago, I've noticed him just beginning to get dominant with other dogs and has started growling and aggressive if they play around. He's fine with people. i want this trained out of him as it's not too bad at the moment so want to nip it in the bud. Has anyone got any recommendations for a decent trainer that can help. I'm in Fremantle. cheers ian