Talk to the coach of the team, or director of the program, that you are leaving and have a frank discussion. I was not pleased with some things that had happened on one of the teams that my son was on and discussed it with the head of the program that he was part of. He made some changes and it resulted in us staying with the program, which ultimately turned out for the best. Sometimes it just takes an honest and open discussion.
I qualify that though with saying that I limit my discussions to things that do not include playing time or how important I believe my son to be. My issues happened to be with the events we were attending etc. as I just have never wanted to be the father who was badgering the coach about playing time etc. But I still maintain that you should address the issues with the current team and give them the chance to correct. Sometimes it works out for the best, as it did in our case...