My Apple ID password

Hello,

This Apple Support article has information about updating your trusted phone number.

Two-factor authentication for Apple ID - Apple Support

“Update your trusted phone number on your Apple ID account page

1. Go to appleid.apple.com.
2. Sign in with your Apple ID.
3. Go to the Security section and click Edit.

If you want to add a phone number, click Add a Trusted Phone Number and enter the phone number. Choose to verify the number with a text message or automated phone call, and click Continue.

To remove a trusted phone number, click  next to the phone number you want to remove.

Update your trusted phone number through account recovery

1. Go to appleid.apple.com.
2. Sign in with your Apple ID.
3. Select “Didn’t get a verification code?”, then select More Options.
4. You'll be redirected to iforgot.apple.com. 
5. Complete your account recovery request. Learn more about account recovery. “

I hope this helps.