How do I reset trust numbers for my Apple Account?

You can see your registered trusted phone numbers when you open the settings for your Apple Account on your iOS device, Mac or on the web:

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• On your iPhone or iPad: Go to Settings, then tap your name. Choose Sign-In & Security, then tap Two-Factor Authentication. Below the list of devices and phone numbers, tap Add Trusted Phone Number.
• On your Mac: From the Apple menu , choose System Settings, then click on your name. Select Sign-In & Security, then choose Two-Factor Authentication. Scroll down, then click Add Trusted Phone Number.
• On the web: Go to account.apple.com, click Sign-In and Security, then choose Account Security. In the Trusted Phone Number section, you can add and remove phone numbers.

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copied from: About trusted phone numbers and trusted devices for Apple Account - Apple Support

If you can't receive the verification code because you have forgotten the trusted phone number, there are different ways to get the code via text message or a phone call from Apple:

Follow the steps, mentioned in the related article:

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If you don’t have a trusted device handy, you can have a verification code sent to your trusted phone number as a text message or phone call.

1. Select “Didn’t Get a Code?” or “Can’t get to your devices?” on the verification code screen.
2. Choose to have the code sent to your trusted phone number.
3. You’ll get a text message or phone call from Apple with your verification code. If you use the Unknown Senders filtering in the Messages app, check there for your verification code.

4 .Enter the code on your other device to complete sign in.

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