Delete old messages: Checkmark this setting to allow the phone to delete older messages in a thread when the Text message limit or Multimedia message limit is reached. Uncheckmark this setting to keep all messages.
Text message limit: Tap to set the number of text messages to save per thread.
Multimedia message limit: Tap to set the number of multimedia messages to save per thread.
Signature: Allows you to enter a signature to automatically send with your messages. Checkmark appears after a signature is entered.
Callback number: Allows you to view or edit the callback number sent with your messages. Checkmark appears after dialog box is closed.