Locked apple id and forgotten trusted phone number

See if anything here helps. If necessary, you can use account recovery as explained in the link at bottom of the article.

Verification code - how to get one and sign in with two-factor authentication. https://support.apple.com/en-us/HT204974

Change Trusted Device list for your Apple ID on Mac - Apple Support

4 Ways to Change the Trusted Number for Your Apple ID on iPhone or iPad

You need another trusted device or telephone number.

See Two-factor authentication for Apple ID - Apple Support:

A trusted device is an iPhone, iPad, or iPod touch with iOS 9 and later, or a Mac with OS X El Capitan and later that you've already signed in to using two-factor authentication.

You have to be able to log into your Apple ID in order to make any changes.

Two-factor authentication for Apple ID - Apple Support

Jan 22, 2020 - You can update your trusted phone numbers when you follow these steps: Go to your Apple ID account page. Sign in with your Apple ID. Go to the Security section and click Edit.

Change your Apple ID - Apple Support