sending text message with iphone? I only get this message when I initiate the conversation. I can reply to people with no problem. But when I try to text someone first, I get "Error Invalid Number: Please re-send using a valid 10 digit mobile # or valid short code." Well...they are valid #'s, one was my mom's and she was sitting right next to me, and what the hell is a short code? I've tried putting the area code in front of the number..no luck. I've tried 1+area code...still no luck. I have a text message plan so that shouldn't be the problem. I paid a small fortune for this phone and it should be able to send texts without a problem!