In this section, you can set and activate the feature to send SMS to any user you missed a call from on their cell phone number. Below are the steps.
Go to Phone System and select Phone Numbers.
Select the number/numbers by clicking the checkbox. Then click the “Edit Selected” button.
You will see a new menu like shown in the image below. In this menu, you need to set Missed call sms value as Yes from the drop-down menu. Once you set it Yes, you will see a new section named Missed call text and you can update the text which you want to send to the user you missed a call from. Once done, click on the update button to save the changes. After this step, the feature will be activated.