Do you have any preferred travel date? So far, I saw there is only one flight on October 14 (Wednesday) and 21(Wednesday), 2009. Maybe the airlines have not published the flight schedule or maybe there will be no flight after Oct 21.
Flight schedule on October 14 & 21, 2009:
19:25/20:50, ZH9849, Shenzhen Airline Full Price: CNY840.

If there is no flight from Shenzhen to Changde on your travel date, you can fly to Changsha and then take a long-distance bus to Changde. Changsha is about 220 km from Changde and it will take at most 2 hours by long-distance bus.

I will make it on June next year, I think i better call the airline for reference, thank you Mr Francisco