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: Checkmark this setting to automatically add a signature that you set.
Callback number: Checkmark this setting to automatically enter a callback number. The default is the phone number, but you can change it to another number.