Zte T230 User Manual page 28

To Answer you will need to touch your
finger tip to the Answer selection and
swipe down.
To Decline you will need to touch your
finger tip to the Decline selection and
swipe down.
To Decline and send them a SMS Reject
message, you will need to touch your
finger tip to the SMS Reject selection and
swipe up, then pick the SMS Quick reply
to send the caller.
The default return SMS can be set at
Dialler > Settings > Other settings >
Quick responses.