My iPhone isn't letting me send/receive picture messages?

I don't know what generation it is but it's the one without the front camera only the back. And ever time I send a pic a little red exclamation mark comes out

  • Why can't I send or receive picture messages? I have a unlocked iPhone 3G with t mobile it won't send or receive picture messages I had the same sim card in my other phone and it sent and received them so it has to be this Iphone how do I fix it or can I?
  • My iPhone 4 won't send or receive text messages? I'm on prepaid and It expired a couple days ago so I bough a card today and put data 25 on (the one I put on every month) and its still not letting me send or recive messages. My Wi-Fi and stuff is working its just the texting.
  • Is there anyway to receive someone else's iMessages but not letting them see your messages? I'm fully aware of the Send & Receive settings in the iPhone, but is there anyway of receiving my son's iMessages but not let his iPhone receive mine? We both share an Apple ID, I'm very suspicious of my son over the past few days, I would like to get his messages but not let him get mine.
  • I can't receive picture messages on my iPhone 4S? I have a iPhone 4S and I have been able to send and receive picture messages since I got it till yesterday I couldn't send or receive any picture I've reset all of my settings turned on the SMS thing and turned on my data thing but I still can't get pictures. How do I get it so I can receive pictures?