https://www.siliconvalley.com/2021/04/26/travel-troubleshooter-wheres-the-refund-for-my-upgrade-on-cathay-pacific/

DEAR TRAVEL TROUBLESHOOTER: I recently requested a refund from Overseas Adventure Travel for an air ticket I purchased through them for a Cathay Pacific flight. I had booked a round-trip premium economy ticket from San Francisco to Hong Kong. A representative from OAT air department recommended this upgrade to premium economy because Cathay Pacific had a special rate. I paid OAT an extra $1,300 for this upgrade.

On the flight from San Francisco to Hong Kong, I was not seated in premium economy. The reason for this action by Cathay Pacific was a change in aircraft. Even at check-in online, the change in seating was not revealed. I was very upset and stressed over this. I paid good money to be seated in a seat of my choice for this 12-hour flight.