What can I change phone number

Welcome and thank you for reaching out. 🤗

According to Apple:

On your iPhone, iPad or Mac:

1. Go to Settings or System Settings, then choose [your name].
2. Tap or click Sign-In & Security.
3. Tap or click your primary phone number to make changes.
4. To remove this phone number from your account, select Remove from Account. If you want to keep the current phone number associated with your Apple Account but change to a different primary phone number, turn off Primary Phone Number.
5. You’re prompted to choose another primary phone number. You can choose one of your other phone numbers already associated with your account as the new primary or add a new primary phone number.
6. Follow the onscreen steps to enter and verify your new primary phone number.

If your new mobile phone number is already connected to your Apple Account as a Messages phone number, shared phone number or trusted phone number, then you don’t need to verify it.

On the web:

The easiest way to change the primary phone number associated with your Apple Account is with your iPhone or other trusted device. A trusted device is an Apple device that’s already signed in to your Apple Account using two-factor authentication, so that we know it’s yours.

1. Go to account.apple.com and sign in to your Apple Account.
2. Go to Sign-In and Security, click Apple Account.
3. Enter the mobile phone number that you want to sign in to your Apple Account, then select Change Apple Account. 
4. A verification code is sent to you at that number. Enter the verification code from the text into the fields provided.

If you need more help, contact Apple Support directly.

Thanks again for reaching out. 👍🏼

Good Luck! 👋🏼😉

Smiliñ 😎 Brian | Community Volunteer

If you want to change your Apple Account phone number into an Apple Account mail address, have a look at these steps:

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Change your Apple Account primary phone number to an email address

You might be prompted to change your Apple Account primary phone number to an email address if you no longer own the mobile phone number being used to sign in to your Apple Account. You can also change your Apple Account primary phone number to an email address to make sign in and recovery easier.

On your iPhone, iPad, or Mac

1. Go to Settings or System Settings, then choose [your name].
2. Tap or click Sign-In & Security.
3. Tap or click your primary phone number to make changes.
4. To remove this phone number from your account, tap Remove from Account. If you want to keep the current phone number associated with your Apple Account but change to a different primary email address, turn off Primary Phone Number.
5. Choose Add New Primary Phone or Email. If you already have an email address associated with your Apple Account, you might be prompted to make it your primary email address instead.
6. You can either choose Existing Email Address if you have an email you can use already, or choose New iCloud Email Address if you want to create a free iCloud email for your account.
7. Follow the onscreen steps to enter and verify your new primary email address. Learn what to do if you didn’t get the email.

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copied from: Using your phone number for Apple Account instead of an email address - Apple Support

For security reasons alteration of phone number and/or primary email address will not always be immediately actioned re the respective fields. Exit SETTINGS and ordinarily I`ve had to wait up to 24 hours for these changes to take effect. This approach is consistent with fundamental security principals.