This issue is pretty scary.. People shifting from iPhone to android cannot receive SMS because it sends as an iMessage ... This is because the user did not turn off iMessage on his previous iPhone.. After searching on the internet, I found this happens because when we send a message, it's first priority is sending it as iMessage and when that's not there, it sends a text.. And iMessage is integrated with the message app.. It automatically sends it.. So the engineering team who is looking to fix this issue will have to fight with simplicity as well as how to get rid if this .. Well as an apple fan, I've given it a fair amount if thought (someone might say let the engeeneering team solve it and you don't waste your time) .. If it's helping others why not put a thought to it.. Apple cannot bring out a new iMessage app, as it will not stay integrated with the message app.. So if the team could somehow separate the iMessage from the text messages, but still integrating them in one app then it would solve it So, When u open the message app, there should be 2 buttons on the bottom, one which says iMessage, and one which says SMS. If u want to send an iMessage to a person, you click on iMessage button, and select or search a contact, like you normally do, but this time, the search will show only people with iMessage. If you want to send a text message, you select the SMS option and then send it as a text.. In this way, Apple can keep iMessage integrated with messages and even resolve the issue. Messaging apps like whatsapp and BBM have a separate directory of the numbers which use it.. So if you don't use whatsapp or BBM, you can't send it .. Apple could separate the directory for iMessage, thus resolving the issue.. Currently there is an option to switch iMessage on.. with my solution, they could just remove the toggle, and making it default.. Only giving other options like which address to receive and the other standard options ... They could turn off iMessage automatically for a number if a SIM card is removed, and thus deleting the Number, which can be used to "send and receive" thus giving only 1 address to send and receive, which is your Apple ID ..So if there is no SIM card, you cannot send or receive an iMessage from/on that number, but can send it only to the Apple ID.. And if there is a SIM card, iMessage will allow you to add a number to send send and receive... It's a good solution and is integrated with the current message app.. And if the user forgets to switch iMessage off, it's not a problem, that's because the moment u remove your SIM card, the number on which to send and received would be removed.. Well if any apple employee, is reading this, it would be nice if you thought about it..