The process depends on how your account was created.

If your account was independent before it was linked to a Studio, make sure you can access the email address associated with it. Then contact Customer Support and request detachment. If Customer Support is unable to process your request, ask your Studio to do so. 

If your account was created by the Studio, Customer Support cannot detach it because the account belongs to the Studio. Ask your Studio to detach the account or create a new account yourself.

Once your account has been detached, you can use it independently.

Note: Models can detach themselves from Studios that have been blocked forever. See this article for instructions.