My iPhone 4 won't send MMS messages?

I just recently got my iPhone 4 last month, so it has the most up to date iOS (5.1.1), however, it doesn't send Multimedia messages (pictures, recordings, and video).It has the camera icon to send them, but when the messages are in the process of being sent, it stops prematurely and says that the file could not be sent. I tried looking for answers to this question elsewhere, but this is the only case I've heard of.

Any help is appreciated.

You might not have the plan for it.
You should check with your service provider to see.
If you do, there could be a setting on the phone for Data or Roaming. Make sure those are enabled, and try sending your message again.

Your iPhone may need its data settings sent back to the phone from your carrier.call their customer care line (usually 6-11) and tell them about you MMS situation. They can have it fixed in a matter of minutes

Turn off Wi-Fi