If you already created a Databox account with your email address and it's not associated with your company's account, you will receive an error when your team tries to add you under their company account in Databox ("User with this email already exists'").
If you don't need the account you're currently using anymore or you've created it by mistake, you can permanently delete it by navigating to Account > Account Details > Cancel my Account.
If you don't want to delete your current account, check out these other strategies you can use to be added to your company's account as well.