Hey does it work? Because I have same situation!
If you absolutely don't get an appointment and have tickets booked for travel, you can walk in really early, as soon as they open up, and request them. You might need to wait for a few hours. I know someone else who tried it this way, I don't remember if it worked. But no harm I'm trying.
An appointment is how i got it done. You could try callong them up. The are very customer friendly.
I am not sure. Usually you have to make appointment, but you can try your luck
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