I'm currently in transit at IST with an onward ticket to Asia tonight. There are available seats in booking class I, so I'm trying to use one of my vouchers to upgrade the flight. Are there no place in the int. departure area where I can do this over the counter? I tried at the lounge, but they couldn't (or wouldn't do it). Are there any TK ticketing office here, where it can be done? I have tried calling CS to do the upgrade, but there is an extremely long line to get through.