My situation is, I bought an att nokia lumia900 without contract. My old number is from T mobile so I choose straight talk , and bought an att micro sim card and port the number from T mobile to straight talk. But after porting, I can make phone calls but I can not receive any incoming calls. The text message function is even more weird, I can send and receive text messages from Att users, but can not either send or receive from other carrier users. I called their CSR for hours they can not figure out the problem and keep telling me since I can send and receive messages from att, there is no problem with my side. anyone can help, desperate here!!!!!