iMessage on 3G connection
iMessage will not allow me to send messages over an AT&T 3G connection, every message is marked "Unable to send" after a short time. However, when my device is connected to a WiFi network there's no problems with sending anything at all. I get the option to send as SMS, but it seems to convert the message to an email which it delivers to the recipient.
Additionally, messages are not received when on 3G but flood in as soon as I hit a WiFi connection.
I've been through the process of switching iMessage off and on, signed out of it and back in, restoring the phone and ensuring my phone number matches my Apple ID details.
Any advice would be appreciated.
Device: iPhone 4, OS: iOS 5.0 (9A334), Carrier: AT&T
iPhone 4, iOS 5