One of the features of iMessage is that it allows an iMessage to be sent as a regular text message in the event that Apple’s servers go down, or if the other party, or yourself, do not have internet at the moment. However it seems that there are reports of iMessage failures in Apple’s Support Communities where users are claiming that some of their iMessages are not sent, or have been unreceived, or sent as a text message on a variety of iPhone devices running on iOS 7. There are also reports on how iMessages aren’t even converted to SMS text messages which could prove to be highly inconvenient for some users of the service.
According to the reports, this is an issue that might have started on the 18th of September, which is when iOS 7 was released to the public, but it seems that whatever the issue is, there are still ongoing reports despite Apple having released the iOS 7.0.2 update. As it stands there is a temporary solution which is to disable iMessage, reset the iPhone’s network settings, and then re-enable iMessage. Some are reporting that this solves their problem but are unsure if this is a permanent fix or a temporary one. Apple has yet to acknowledge this issue, but hopefully an update will be issued soon to correct it.