Iphone 4 iMessage isn't working?

My iphone 4 won't send any iMessages. It can send regular texts, but not iMessage. I have tried turning iMessage on and off, and restarting my phone, but it won't work.a friend of mine suggested that I reboot my phone, but my lock button doesn't work. Is there any way to fix my iMessage?

This has happened to my iPhone 4 but keep on turning it off and on ( iMessage toggle ) and let it sit for a while and it will work!

1) Check if you have internet connection - perform a google search with the safari on your iPhone - if google.com loads - internet connection is good

2) Check if the person you're sending to has iMessage enabled. Did it use to work before?

3) Toggle iMessage off and turn it on and leave it there for a while until it says it's active. Go to iCloud settings and sign in with your Apple ID.

4) Try to send a message to a verified iMessage user (Wait for send button to turn blue)

5) If all of the steps above does not work, perform a backup on iTunes and restore to the backup.

6) Still doesn't work? Setup an appointment with an Apple store genius.

Consider plugging it into your computer assuming you have an Apple computer. Shut off the computer then do a restart. See if the phone responds. It should. Check to see if you have a software update too.