You can select one of the three default Reply Now messages to send to a
caller instead of answering an incoming call. You can change the default messages or
compose a new Reply Now message.
In the Phone app, swipe down
from the top of the screen.
Tap > Reply Now.
Tap the message you want to change.
Type a new Reply Now message.
To prevent the Reply Now icon from appearing when you receive an incoming
call, set the Reply Now switch to