When you place a phone call using YAPI Mobile app or YAPI UH app, YAPI uses your office phone number as a caller id (or any other phone number you want YAPI to use as a caller id). To setup a caller id number, launch YAPI, open Global Configuration, go to CT tab, and enter your Practice number. Click Verify button.  YAPI will give you a numerical code to enter when YAPI  calls your phone, in order to verify that the phone number you gave is correct.
Untitled-1

Click Ok button, answer the call, and enter the verification code.