Changing the trusted phone number

Please follow these instructions

To see, add, or change your trusted phone numbers:

• On your iPhone, iPad, or iPod touch: Go to Settings > your name > Password & Security. Next to Trusted Phone Number, tap Edit.
• Choose Apple menu  > System Settings (or System Preferences), then click your name (or Apple ID). Click Password & Security, then add or remove a trusted phone number.
• Go to the Account Security section of appleid.apple.com.