Thanks for the inquiry.
For account and billing related issues, please reach out to our support team directly here for your 'Account or billing' issue, here: https://support.roku.com/contactus. They will be able to further assist you.
In addition, we would recommend creating a PIN for your Roku account to avoid any further unwanted purchases on your account. For more information about how to create a PIN, visit our Support page here: How do I create or update the PIN for my Roku account?