iPhone can't send/receive photo texts from non-iPhone users

I've noticed a lot of other people with this same problem and so far nobody has a solution. I've tried resetting my iPhone 4 and was on the phone for an hour with AT&T last night to see if it was a problem on their end as someone else had mentioned. Nope. Basically, I can't receive any photos through text messaging (MMS) and I can't send any photos through text messaging with anyone who doesn't have an iphone. I used to be able to. Not anymore. Doesn't matter if I'm on wi-fi or cellular. I've checked to make sure I've got MMS on. I do. I've reset network settings, we've even switched radio towers to try that. Nothing.

Can someone help?