Thanks. I was kinda suspecting it wasn't going to change.
Part of what is confusing me is that I can't find any indication of why it won't unlock (even with the IMEI). That's annoying by itself but it also means that, had I tried to vet this phone moru carefully based on the imei, I still wouldn't have caught this.
What do you do to verify that a phone is unlockable? What should I check in the future?