How do I get my old (non-iOS) number off of imessage?!

I recently sold my iPhone 3GS and ported the number out to Google Voice. This old number is now forwarded to a new number on an employer provided 4S. I figured I could save some money, avoid the hassle of carrying two phones, and, at the same time, keep my personal number. I read about all of the problems that would happen if I did not turn off imessage before porting a number away from iOS and was determined to not let it happen to me. Well...it happened anyway.

Before doing anything, I SHUT OFF iMESSAGE. I then ported the number out and cancelled my account, removed the SIM (AT&T), did a complete wipe/restore of the iphone, unregistered the iphone from my support profile, and sold the phone. From what I can tell from all of the support forum posts, I did everything I was supposed to do to ensure I would have no issues with imessage. I was so sure of myself, I didn't even bother to test it. I wish I had.

Despite my efforts, I am still not receiving text messages from iOS imessage users because messages from them to me still default to imessage instead of SMS. It doesn't seem to matter if they have the "Send as SMS" option toggled on or off...I will not get the message regardless. I've had people delete entire message strings and delete/replace my contact info in an effort to fix. No luck. I even had a stranger at work who did not have my contact info test it out for me. When he tried to text me, it defaulted to imessage. I must point out that I have ZERO issues receiving SMS messages.

How can this be? And how do I go about correcting the issue? I've already spent about an hour on the phone with Apple and about an hour at the genius bar (where the issue was successfully demonstrated first hand when a "genius" tried to text me from his phone). They claim that they had no prior knowledge of any issues with imessage and suggested that I tell all of my contacts with iphones to simply "just remember" to send me SMS only. Seriously? This is an unreasonable request...and certainly not a fix. After arguing for a while, they took my contact info and "escalated the issue to engineering." It's now been three weeks and I've heard nothing.

Any suggestions? I'm guessing that someone, somewhere at Apple can somehow remove the association between imessage and my old number from the server...somehow. Any help would be appreciated, especially any help regarding how to successfully escalate issues within Apple support.