A friend of mine has recently "upgraded" his mobile phone from an iPhone to another, non-iOS device. However, sending them a message from my own iPhone continues to send as an iMessage.
The "Delivered" message does not seem to appear under my sent message, and indeed the message never reaches its recipient, but also Messages [the app] seems to not be able to decipher if the message reached its recipient or not, and as a result does not resend the message as a standard SMS. Instead, I have to manually tap and hold on my message and select the "Send as Text Message" option to resend.
Does anyone know how to resolve this issue? Or is it a bug within iOS?
Currently running on iPhone 5 on iOS 6.0.2
View the Correct Answer Messages appear to send as iMessages despite contact not having an iOS device anymore in Solve the iphone problem , iPhone Phone and Messaging errors Answer