Custodial account ownership specific situation?

I am 18 years old, and am interested in knowing the if and how legally I can/can't take ownership of a custodial account set up for me when I was born. The facts are that the account was set up around when I was born, money was put into the account by my grandparents, my father was the custodian, and my mother was the broker. The account was created and held in California initially with dean witter. The account was moved to A. G. Edwards, along with all the brokers accounts, then moved again to Merrill Lynch (also to a new broker). There were no special reasons the account was set up for me to be 25 other than convenience of control. Now the opinionated information, when the account was moved to A.G. Edwards, it was claimed by the broker that A.G. Edwards changed all the accounts to age 18 (except mine) because it was not legal unless done so through a will or by court order. A.G. Edwards claims that the account legally should be mine, and Merrill Lynch claims the account is under custodial control until I am 25 (though they have no physical doentation as to why, and are unsure how it can be set that way). I hope that explains the situation, I would like if answers have physical sources that can prove to Merrill, and the custodian the legality of the issue, along with a synopsis of what the sources say. I know that the account can be mine if the custodian is convinced to quit by a lawyer in a court of law (ume this is not possible due to extenuating cirstances), I believe (not sure) that the account can be mine if Merrill Lynch is unable to provide doentation in a court of law (possible but hopefully their is an easier method). ume the account is valuable enough to make this situation worth looking at. Lastly a opinion can't help me, telling me I should just let the account stay as is will be irrelevant information. Sorry for the tough situation, but I hope to get some help to clarify what should be done.