Originally Posted by
Cathay Boy
You can? Last time I had M class ticket and I wanted to use my miles to upgrade and I told the agent I'm willing to pay the difference up to K, and he simply looked at me with a blank stare and say "can't adjust class differences even if you are willing to pay"
You can...but in a round about way. You basically need to get a refund for your original ticket, pay any cancellation fees, and then buy a new ticket in the new class.