There are some scenarios in which you may want to allow a number to be uploaded multiple times against different names (e.g. a school that needs to contact a parent on one number but referring to two different children in separate messages).
By default, the Web Portal will automatically restrict duplicate numbers from being uploaded; however, this can be changed to allow duplicate numbers to be uploaded
Go to Account, then Account Settings:
To allow duplicate contacts, click on the toggle switch next to "Allow Duplicate Contacts":
NOTE: Once you have turned this on, you will need to contact support (email@example.com) if you want to turn it back off.