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 Messaging Hub will automatically restrict duplicate numbers from being created; however, this can be changed to allow duplicate numbers to be created
How to Allow Duplicate Contacts
1. In the menu, click on the icon, then select Account:
2. Select the General tab.
3. Find where it says Allow duplicate contacts and toggle the switch to On: