For next time, if there is one, never accept paying at the airport - it's a recipe for disaster. It merely means the the phone agent is too lazy to do it for you. I have fallen for it a few times but now I always insist that it is done on the phone. Just recently, I tried to change a VS flight on an EK issued ticket. The agent said "call VS," I responded with "VS won't change it without a VS PNR#, can you give me that?" (they couldn't)
then they said to to go to VS at the airport to revalidate the (EK) ticket.
I hung up and called back till it worked out.
Cheers,