The Phone Field Setting feature enables you to configure a text or formula (that is being used as reference to from another object) to behave as data that the Phone Field can interpret. This field will be added to the “Select Phone Field” dropdown list.
How To: Create a Custom Phone Field.
Click on “SMS Phone Field Setting” Tab and Click on “New” to create a New Record.
On the “SMS Phone Field Settings” page, Click “Select Object” drop down box to select a standard or custom object.
Let us Select “Contact” from the “Select Object” Drop down box, moving down - select a field that you have assigned a Phone Number in the “Select Field where you are storing phone number” drop down box.
Here we’ve selected “Account Phone” which is a formula (referenced to account phone field) field of contact.
The "Field API Name" gets populated based on your selection.
Select the “IsActive” checkbox and click on Submit.
To Verify above settings, Click on Contact and open a record. Click on “Send SMS” button to open a new window.
Under the “Select Phone Field” drop down box, the “Account Phone” field should reflect.
Features the Stand Out!: