AT&T Refuses to Unlock Phone After 3 Years

I have an iPhone that was on a corporate account for about 3 years.  When I left company, they let me keep the phone since it was paid for after 2 years.  I decided to keep AT&T service but switch to a pre-paid account.  Someone at my local AT&T store helped me move everything over the the personal account and said that it wouldn't be a problem having the phone unlocked.  A few days after he put in a request to unlock the phone, and I get an email saying that it couldn't be unlocked since I hadn't had AT&T service for 6 months. 

I've talked to a couple other customer service reps since then, who have told me that it shouldn't be a problem, but the same thing keeps happening.  Of course, if the phone would have been unlocked before switching from the corporate to the personal account, there wouldn't be any issue.  Is it even worth my time continuing to try to have it unlocked at this point?  I'm leaving for a trip to Asia in about a week and was hoping to be able to drop in a SIM and use the phone while traveling.