I know there's a couple of threads with the same problem however, none have helped me or have been similar to my problem.
I have a Sprint BB Tour but I have an At&t sim card in it.
I used to have an At&t BB Bold and it worked fine! I had no data plan & I was able to talk, text & send mms.
Now that I have the Tour I can't send mms. I just get the red x. I know people say I need a data plan, but I was able to send & receive them on my old bb without it. Any help is greatly appreciated!