There may be phone numbers that you no longer want to associate with your account's two-factor authentication system.
Apple's two-factor authentication system bypasses access to the Apple ID account by requiring that, in addition to the password, you must also provide a code that reaches a trusted device (an iPhone, iPad or Mac) or a trusted phone number (one that has been verified after being added).
Trusted devices are an easier set to manage because they represent all devices connected with the same Apple ID for use with iCloud. Reliable numbers are something else.
It's easy to remove a trusted number, but first make sure you can access the trusted accounts on the account. If not, it may crash.
To verify the trusted devices paired successfully, try logging into the Apple ID website.
Always requires a second factor code to access account details if a stored identity is not used on supported versions of iOS, iPadOS or macOS and Safari. When you do, you'll get a warning on all trusted devices that will notify you that someone is trying to access your account, with a small preview of a map and two buttons: Allow or Don't allow.
To authorize access, tap or click Allow, enter the code that appears in the appropriate places on the Apple ID site and confirm that the login was successful.
If you don't get the Allow / Don't allow message on any device, there is a problem.
Two-factor authentication may have been set up for an Apple ID account that you aren't signed in to on an iPhone, iPad, or Mac.
In this case, a trusted device must be associated with the account in order not to inadvertently lose access by deleting a trusted phone number.
If you have only one Apple device, I recommend that you add a phone belonging to another (trusted) person in case of problems with your device, without losing access to authentication.
It is recommended that you use a secondary account on a Mac with the iCloud account set as the Apple ID. (An iPhone or iPad can only be associated with a single Apple ID for iCloud; on a Mac, each account can have a separate Apple ID associated with iCloud, but they are only active when you log into that Mac account.)
Once done, log into that Mac account and check the message and two-factor code. Otherwise, you need to use an existing trusted phone number under your control to set up that secondary Mac account.
Once we have confirmed that we have received the message, we can delete a trusted number that we do not want to keep:
• With iOS or iPadOS, or with Settings> Account name> Password and security, then tap Modification next to the label Trusted phone. Tap the red button to remove the phone from the list and confirm the removal.
• On macOS 10.14 Mojave or earlier, visit Preferences of System > iCloud> Account Details> Security, select a phone number and click the minus (-) button to remove it. Confirm its removal by clicking Remove.
• On macOS 10.15 Catalina or later, go to Preferences of System > Apple ID> Password and security, click your Modification next to the Trusted phone number label, select the phone number, then click the minus (-) button to delete it. Confirm its removal by clicking Remove.
• On the Apple ID website, log into your account and click the button Edit next to the Security section, click the “x” next to a trusted number to remove it and finally confirm by clicking Remove.