Q: How to restore iMessage after sms

Hi torefra,

Thanks for using Apple Support Communities.  This article has some steps you can take for issues with sending iMessages:

iOS: Troubleshooting Messages

http://support.apple.com/kb/ts2755

If you are still unable to send or receive an iMessage, follow these steps

1. Make sure that the contact trying to message you isn't blocked in Settings > Messages > Blocked.
2. Verify that the contact you are attempting to send a message to is registered with iMessage.
3. If the issue occurs with a specific contact or contacts, back up or forward important messages and delete your current messaging threads with the contact. Create a new message to the contact and try again.
4. If the issue occurs with a specific contact or contacts, delete and re-create the contact in the Contacts application. Create a new message to the newly created contact and try again.
5. Back up and restore your device as new.

Cheers,

- Ari