Authorize new phone

 If your iPhone is your only trusted device and it's missing or damaged, you won't be able to receive verification codes required to access your account.

Two-factor authentication for Apple ID - Apple Support

If you can’t sign in, reset your password, or receive verification codes, you can request account recovery to regain access to your account. Account recovery might take a few days or longer, depending on the specific account information you can provide to verify your identity. For more info, see:

Get a verification code and sign in with two-factor authentication - Apple Support

Missdavis0405 Said:

"Authorize new phone: i lost my IPad and IPhone, I’m trying to sign in on another phone using my Apple ID but it’s asking me to verify by checking my other device. I don’t have the device to verify. I tried signing in on a computer and it’s doing the same thing. How do I authorize my current phone?"

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Sounds like you may need to add a Trusted Device.

1. Go here: Manage Two-Factor Authentication for your Apple ID from iPhone - Apple Support
2. Scroll to: Add another device as a trusted device

To Get the Phone Number Changed...

Contact Apple Support: Ask the Apple Rep to modify it over the phone. If permitted to do so, then inform to modify the Phone Number associated to your Apple Account, to what it should be. Important: Perform a Trial & Error login session with the Apple Rep prior to ending the phone call.

Contact ApleSupport. 

• Contact Us - Choose Locations
• Proceed from there as Necessary
• Why the Wait: Phone calls are taking a bit to go through at the moment, due to lots of calls. With the Coronavirus Pandemic, many are at home at the moment, with much time on their hands to contact Apple. So, just stay on the line, and you will get through :)