Step 1: Log into your TMS

Step 2: Click on PBX Manager

Step 3: Click on PBX Settings

Step 4: In the very first dropdown box, select the number you would like as your Default External Caller ID

Step 5: Uncheck the box that says Allow Personal Caller ID

Step 6: Now click the Update PBX Settings button. Allow 8 minutes for this change to take effect