If you have found yourself missing text messages after you switched to an Android or Windows Phone device from an iPhone, Apple is helping you out with a little tool that will deregister your phone number from iMessage. The issue apparently is that Apple routes your incoming messages to iMessage so when you make the switch, texts from iPhone users disappear into the ether. Apple wants to note though that traditional SMS are not routed through iMessage servers.
If you forgot to disable iMessage before switching phones, the only available solution before was to completely disconnect your device from an Apple account. Now, you just need to input your number into Apple’s deregistration site and put in the verification sent to you.