This wikiHow teaches you how to remove a secondary cell phone number from an Apple ID account using an iPhone.
Step
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Step 1. Open Settings on iPhone
This gray gear-shaped app is on the home screen.
This application can also be found in the "Utilities" folder
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Step 2. Scroll down the screen and tap iCloud
This option is in the fourth group of menu options.
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Step 3. Touch your Apple ID email address
It's at the top of the device screen.
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Step 4. Sign in using your Apple ID when prompted
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Step 5. Touch Contact Information
It's the first option under Apple ID.
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Step 6. Touch the mobile number you want to delete
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Step 7. Touch Remove Phone Number
Note: Phone numbers that have "Primary" written next to them cannot be deleted. This means that it is the only Apple ID phone number stored in your account
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Step 8. Touch Remove
Your friend will now no longer be able to contact you using that number through Apple services, such as iMessage, FaceTime, or iCloud Sharing.