I'm going to go out on a limb here in the hopes that somebody will have a simple solution since I haven't been able to get any answer from my carrier (Straight Talk). I have an iPhone 3GS that was originally on the AT&T network, but is now using a Straight Talk SIM with their "Bring Your Own Phone" program. I have never been able to get MMS messaging to work. I get the run-around every time I try to contact ST. I have settings in the iPhone turned on for MMS messaging and data works fine as well as SMS messages and iMessage. I'm no iOS power user and use the phone mostly for basic phone functionality, but it sure would be nice to get MMS working since I just can't afford a newer iPhone at this point. Like REALLY broke here.