Regain access to Apple ID protected by 2-step verification after losing access to trusted device
You can take the following approach one-by-one:


If you have lost access to the phone number associated with your Apple ID for 2-step verification, you can regain access to your account as long as you remember the password and you happen to have access to your account Recovery key.

You'll need to visit Apple ID account page, enter your Apple ID and password, and on Verify Your Identity screen, you'll need to select Can’t access your trusted devices? You'll be asked to enter your Recovery Key.

For detailed instructions, you can refer Apple Support article, If you can‘t sign in with two-step verification using your Apple ID.
If you do not have the your account Recovery Key, your second resort will be to contact Apple Support. You can find the contact information for your region, by referring to this Apple Support document, Contact Apple for help with Apple ID account security.