How to remove your phone number from iMessage if you switch to Android

[iMore.com]

If you've switched from iPhone to something else, like Android, and aren't receiving text messages, it could be that your phone number is still registered with iMessage. If that's the case, Apple has an online tool you can use to deregister with iMessage and get your SMS/MMS working properly with your new phone.

Full story from the iMore Blog...