Me and my eldest DD were in the same boat. We could not change her name and now for the first time in her life she is forced to use her fathers surname (what's on her birth certificate but she has never been known as that and her medicare card has always been different to her birth certificate) and there is nothing we can do about it. Her father saw her twice in 8years and we still couldn't change her name. She is now 13 and cant change it legally until she is 18 apparently.