To delete your phone number from your account:
Open the Safepoint app
Ensure that you are logged into an account
Tap the 'Account' button at the bottom right
Tap 'Profile'
Tap 'Contact'
Tap 'Delete'
Confirm by tapping 'Yes' in the popup
Your phone number is now deleted!
Note: to re-add another phone number, follow the Adding a phone number article.