I am trying to update my credit card information but it just says my account has been locked.

If your Apple ID is locked or disabled - https://support.apple.com/HT204106 - "If you or someone else enters your password, security questions, or other account information incorrectly too many times, your Apple ID automatically locks to protect your security and you can't sign in to any Apple services."

What to do after [or before] you change your Apple ID [email address] or password - https://support.apple.com/HT204071 - "After you change your Apple ID email address or password, you might need to update your sign-in information with any Apple services you're using." - Or if you're seeing persistent disabled messages or repeated requests for the password to your previous Apple ID.

If you cannot resolve it yourself try one of these contact methods:

- Click here --> https://support.apple.com/choose-country-region/media-services Select your country, then a product.

- Contact Apple for help with Apple ID account security - https://support.apple.com/HT204169

- Contact Apple for support and service - "See a list of Apple phone numbers around the world." - https://support.apple.com/HT201232