We live in NC but we just went through the same thing. Eventually, we were able to get his mother to help us change the name but at first she said no. You have to file a "Prayer for relief" through a Special Proceeding in Superior Court. That is what we were gonna do before we got her to agree. I don't know if it is the same in your court, but I'm sure there is a way that you can find out. Look at other court cases about the same issue or just look in the legal reference books at your local library. You should be able to self file this motion. You can also look on the internet for sample filings and copy them.
You and I seem to have alot in common....Good Luck!