I switched from an Iphone 5 to the N3 and all of a sudden stopped receiving any text from any iphone user from the past. So I took the following steps to try and fix the situation: I had unregistered my Iphone 5 on Apple's website and the text stopped going to the Iphone. However, then it started going to my Ipad. I unregistered the Ipad, so it stopped going there, however, when someone would send me a message from an Iphone, it would come up on their screen undelieverable. To fix the issue, I had to have them turn off imessage and turn on MMS. For me, I had to do both, unregister the devices and have the senders turn off imessage and turn on MMS.