How can I send a text message to someone if I cannot answer a call on my Nokia device?

Select Menu > Tools (or Ctrl. panel) > Settings > Phone > Call > Reject call with SMS (or Reject call with message) > Yes.

To write a pre-defined message, select Call > Message text and enter the text.

To reject a call with the text message do the following steps when someone is calling:

  1. Select Silence (Right Selection key).
  2. Select Send msg. (Right Selection key).
  3. The text message editor opens with a pre-defined message. The caller number or name is automatically updated in the TO: field.
  4. Select the call key (green key) to send the message.
  5. Select Reject either by using the Right Selection key or the end key (red key). 

Start from step 2, if Silent is the active profile on your device.