After replacing my iPhone 5 with LG G2 some people could not send SMS using iMessage from their iPhones to my new LG G2, because their iPhones keep trying to send through iMessage even though I turned it off before replacing my iPhone. The only way to send SMS was to turn off the iMessage on senders’ iPhones. Here is the fix that I found on Apple Support:
1. Go to https://supportprofile.apple.com/MySupportProfile.do
2. Log in with your Apple ID
3. Click “Edit Products”
4. Find your phone and click “X” to the right of the product
5. Click “Unregister”
Then go to https://appleid.apple.com/cgi-bin/WebObjects/MyAppleId.woa/
Click on “Reset my password” and follow instructions.