Actually, it just so happens that I went to the doctor today, found out something pretty concerning, and went back to work thinking, "OMG, why on earth did I change from the PPO to the HDHP for 2016???" So I went to my HR/benefits people right away and asked if there was any way that I could change my 2016 election back to the PPO. Sure enough, they said it was not too late because the coverage period had not started yet. They just needed to have me re-complete the form with my changes. Yay, all set! So, I'd say that for you, it's also worth a try!