This feature is located in the “Advanced Options” section. Please refer to section "Creating/Editing a Click to Call button"




Scroll down to locate the following option : 


-"Call the user first and wait for an answer" : This will call the end-user (client) first. If the user does not answer, the business will not be called, except if the call reaches the user's voice mail.
-"Call the business first and wait for an answer" : This will call the Business first. If the business does not answer, the client will not be called unless the call reaches the business's voicemail.