Use Messages settings to adjust settings for SMS and MMS messages.
NOTE: MMS is available only on iPhone 3G or later. The MMS Messaging and Show Subject Field settings doesn’t appear if MMS isn’t supported by your carrier.
Choose Messages and turn Show Preview on or off.
Choose Messages and turn Repeat Alert on or off. If you ignore a message alert, you’ll be alerted two more times.
Choose Messages and turn MMS Messaging on or off. If MMS messaging is turned off, you won’t be able to receive MMS file attachments such as images or audio.
Choose Messages and turn Show Subject Field on.