I was able to do this successfully for a United ticket! I emailed the local office, they gave me the amount of taxes and fees ($117 for a $347 ticket), somewhat high but still not bad for 20,000 miles that are about to expire 12/31. They did require a few strange things like a credit card authorization form, and a signed turkish airlines form approving the use of the miles, and pictures of the credit card and my driver's license. This is still better than going to the airport to pay though. Within an hour the ticket was issued. The responsiveness of the staff was really quite incredible and I think I will book all my tickets through the local office going forward.