Apple’s iMessages app makes it possible for users to communicate from one iOS device to another without it counting against text messaging. The service registers a user’s Apple ID and iPhone phone number so that messages can be sent and received between all iOS devices, including iPad and iPod touch.
Unfortunately, ever since Apple launched the service in 2011, it has caused a bit of a raucous for people that switch from iOS to Android or Windows-based phones. Some users have experienced lost text messages from contacts that still use iMessages. It appears that messages are rerouted back to Apple’s iMessages service instead of going directly to the person’s new mobile device.