AT&T still going by September 25th deadline for iPhone MMS
AT&T spokeman Mark Siegel was adamant about the September 25th deadline. "September 25th is still the date that MMS will be available to iPhone users," he said, "We can't comment on what people might have been doing" to get MMS to work in the meantime. One thing that those with working MMS function have in common is that the recent OS upgrade to 3.1 for the iPhone also updated the AT&T carrier profile to version 5.0. You can try to update this on your device to see what happens, but again, you do risk losing the phone part of the iPhone and walking around with just "i" is not going to help you stay in touch.
Apple iPhone 3GS Specifications | Review
source: TUAW, USATODAY