To display the Ignore with message option on the incoming call screen, enable it in the Settings menu.
From the Home screen, touch and hold the Recent Apps Key (in the Touch Keys bar) > Settings > Call > checkmark the Allow ignore with message checkbox.
If the screen is unlocked, tap the Ignore with message icon .
If the screen is locked, swipe the Ignore with message icon in any direction.
Tap the text message you want to send in place of answering the call.
This feature can only be used to send a message to another mobile phone. It's not applicable to incoming landline calls.