I'm on my way home from LAS and was hoping to do a SDC onto an earlier flight... I arrived at LAS about 3.5 hours early for my flight and got into the Skypriority lane, awaiting my turn to check-in. Upon checking in, I asked the customer service agent at the desk to please check what flights I could SDC onto, which would get me home earlier than my current itinerary. She responded, "don't even try it -- there's nothing available -- it doesn't matter one bit that you're a diamond medallion..." For reference, I checked earlier while at the hotel and saw there were plenty of available seats on myriad flights that would get me home at the very least 1.5 hours earlier. I said this to the agent and she goes, "no you're wrong," and handed me my boarding passes. "NEXT!" she shouted and she then told me the exit was to the right and to go up the escalators to the D gates. What if any recourse do I have? What should I do? Call the DM line? Email Delta? Nothing? Any opinions appreciated.

Thanks!