Whenever I'm out of wifi I can't receive text messages from other iPhone users. I can only iMessage when I'm in wifi, before updating my phone to the iOS 7 my phone would automatically send iMessages as text messages to me when I was out of wifi.

Hello Deeelyynn,

Thanks for using Apple Support Communities.

For more information on this, take a look at:

iOS: Troubleshooting Messages

http://support.apple.com/kb/TS2755

If you still can't send or receive iMessages

1. Ensure that iMessage is turned on in Settings > Messages.
2. To send and receive iMessages, your device must have a valid cellular or Wi-Fi data connection.
   • iPhone: Troubleshooting Cellular data
   • iOS: Troubleshooting Wi-Fi networks and connections
3. iMessage registration validates your Apple ID for use with iMessage. If you are unable to activate iMessage, follow this article.
4. If an iMessage cannot be sent, it will be resent using SMS or MMS, depending on the content. You can turn this behavior on or off in Settings > Messages > Send As SMS. Carrier messaging rates may apply.
5. Verify that the Apple ID or phone number is listed in Settings > Messages > Send & Receive.

Best of luck,

Mario

Comforting to know I am not he only one with this issue. It was never a problem untill the latest update. I have discovered that the choice to send as SMS if not connected to wifi is not defaulted in your settings. As i have the old 3Gs phone the upgrade to 7 was not applicable to me but it was to my friends. I had my friends look into it and they all turned it back on and problem solved.

Settings

Messages

Send as SMS (have this ON).