I can't figure out how I upgraded my ticket!

[niteray]

So, after a long while since travelling anywhere, a few months ago I decided to splurge and bought a ticket on Cathay to LOS, while the basic Economy ticket was relatively low.  I had been stalking the prices, as a habit for years, and discovered this ticket at a reasonable price. As a treat for myself, I bought the final leg ( HGK to YYZ ) as Premium Economy.

I informed a travelling buddy of my discovered ticket on Cathay, and he too bought the exact same flight, including the Premium Economy final leg. Everything seemed good.

Recently, while stalking the flight prices again, I discovered that base flight price on Cathay had jumped up more than a few $$$.  While playing with the google flights, I later discovered that price for Premium Economy had lowered close to the price we had paid for our original tickets. 

I freaked a bit, then tried to upgrade my ticket to Premium Economy both ways, instead of only one.  I was unsuccessful the first night I tried, first by trying to upgrade it online, then I tried calling the customer service #, then I tried the chat app.  Customer service put me on hold, then cut the call.  No one ever responded to the chat app on the Cathay website.

The next morning, I tried the Cathay website again, and I easily managed to upgrade my ticket by paying a few $$$ online, without any assistance.

Problem: I told my buddy about the successful upgrade and advise he do it as well.  He tried it thru customer service, who told him complete nonsense about paying more than the advertised price to add to our already paid ticket to full Premium Economy.  He tried another person on customer service person, who told him to add a lesser but still large amount to upgrade his seat.  He tried it online without any success. 

I tried it as well, but was unable to remember how I did it.  I do remember how easy it was to finally get it done but now, I don't know where i clicked to get it done.  So it looks like I'm flying on a different cabin than  my buddy, if he can't figure out how to pay the small amount I paid to get upgraded