Two things to try as a suggestion,
1. Provided you registered your iPhone with Apple -
To deactivate iMessage, you will need to unregister your phone from your Apple ID:
Go to
https://supportprofile.apple.com
Log in with your Apple ID and password
Select the product you need to de-register (your iPhone, for example)
Click ?Unregister?
You will see the message ?Are you sure you want to unregister and delete this product?? ? Click ?Unregister? again
Your iPhone will be removed from your Apple ID and will no longer receive iMessages.
Or
2. Log into your iCloud account from a Pc or Mac and change that account password. ITunes and iCloud can use your same apple ID but in some cases different passwords.
Most people have reported one or the other of these methods worked for them. Once set up, iMessages ties itself to your phone number and email addresses. Sometimes it takes a few minutes to an hour or more for the change to be reflected on the server end of things.
One last suggestion that may seem a bit odd. Borrow one of your friends iPhone 4 or 4s ( iPhone 5 won't work cause it uses a nano sim ) and put your SIM card in the iPhone. Reboot the iPhone and it will think its you, now you have to turn on / activate iMessage with your Apple ID and after its activated then turn it off. This is a bit extreme but should work if all else fails.
Hope this works for you.