Just turned 21 and looking to gain access to my custodial account that was set up for me

So when I was in high school I had a custodial brokerage account set up for me that I never really saw or had control over but all the money going into it was money from work, birthdays, and holidays etc. Now, my parents are basically refusing to turn the account over to me and from my research and what I can understand, they need to fill out some forms in order for me to have access to to it; which they are not willing to do. Is there a process that I can go through to claim the account? I also tried logging into it but the phone number they have on file is my dad’s and not mine so I cant get the confirmation code. If it helps I’m also pretty sure its through Charles Schwab. Any advice would be helpful!