Ok, so options here:
1) Call up and ask to be put on standby for K class on the flight you want. If it opens, you'll be confirmed into that class and get a confirmed seat. According to FT, this happens within T-3 hours of the flight.
2) Go to the airport, go to the gate of the flight you want to fly on and ask to be put onto standby for their flight. They will add you to the list and sometimes inform you of your chances. This will not change your return flight and you risk not getting onto the flight. I would check the standby list on the flight status to see how many people are standing by. You may also be able to be added to the list on the phone, but I have never tried that.
Good luck and report back.