I'm looking into upfaring from P (discounted economy) to M/Y/I so I can have the EQMs added to my Alaska account. The ticket was booked through a 3rd party agent. Last time I talked to Hainan's customer service I was told this can be done only through the agent with whom I booked the ticket, or at the check-in counter at the airport. The customer service representative didn't sound professional or confident of this though.

Instead of going through the 3rd party agent again (who has really bad customer service and slow response), can I do this at the check-in counter at the airport? Has anyone done this before?