My Iphone 3gs was stolen. I got a new sim card and kept my same number, however, when anyone from an Iphone tries to text message me, it turns it into an imessage and goes to my stolen phone so the person with the stolen phone is getting all of my message

Easy! Change the password of your Apple account. Then the stolen iphone not login!

If you wanted to go completely safe, then you can also change your email address also is associated with your Apple account.

Yes. Change the password. NOW! In fact, change ALL of your passwords. If you had any sensitive information stored on your phone, like credit card numbers, etc., notify the card issuers that they may have been compromised.

I do not ask?

Settings>Messages>Receive At...you need to remove the email address you have listed here...I'm assuming you've deactivated the sim card of your stolen phone, correct?

It sounds to me that there are two mobile phones with the same number !, surely that cannot happen

I cannot see that changing the apple password can help, the problem is with two active sim cards having the same phone number.

Give the phone number a ring on another phone with your phone switched off then the chap who pinched it may answer your call

Tim

You know the person who stole the iPhone?

He was recommending you make this change on the replacement iPhone.

My boss was upgraded to an iPhone 4S from an iPhone 4 running iOS 5.0.1

Prior to the handset swap, he reset all settings from the device. Despite doing this, the old handset continues to receive iMessages which were associated with his iMessage account (presumably his AppleID).

Shouldn't resetting the phone in this fashion have resolved the issue?

The owner of the phone mentioned in this article completed a remote lock/wipe of her phone, and it seems to have exhibited similar behaviour:

http://www.theregister.co.uk/2011/12/15/imessage_persistant/

Has anyone found a reliable method for ensuring that iMessages won't be delivered to a lost/stolen/replaced device?

Update: I read this thread, and seems as though it could be useful, and I guess explains why a remote lock/wipe may not have worked as mentioned in the last article (because the original SIM was in the phone)?

How is it that you know that the stolen phone is receiving messages? And how do you know that changing the password did not fix the problem.