How is it different from the automatic reply?
The automatic reply sends the text with no action from you, shortly after each missed or rejected call. Manual reply waits for your decision: nothing goes out until you tap the button. Both use the same template, the same history and the same safeguards, such as the STOP list. Many people start with manual reply to see how their customers respond, then switch on the automatic mode once they are happy with the message. You can also keep manual reply for the days when automatic sending is off.