Changing rate question

My son a senior in high school aged 17 and is in the dep. When he went down to take is asvab testing he failed the depth perception test. He wanted to be an aviation machinist mate but couldn't qualify because of the failed dpt test. We were told that he could get an private eye test and that if he passe it would qualify him for aviation rates. He passed the next day with flying colors. He signed up for an advanced weapons system rate with the understanding that he could change anytime before he left for boot. It has been a couple months now the recruiter was at the house last night and still doesn't have his rate changed. Are we getting the run around here or would it really take this long to change his rate. I was also told that since he is a minor that his mother and I can cancel his contract at any time before he leaves for boot. He will turn 18 in May and we are concerned. Any advice would be greatly appreciated.