I called them again. The first person I spoke with told me I had to pay the difference fare which was 7-8k. The second person told me my economy fare wasn't elegible even to pay the difference fare. I see in expert flyer that some weekday flights are leaving with all seats empty in business or only 1-2 taken. I can't believe they'd rather leave them empty than make some money. If you get an upgrade please keep us posted. Thanks.