This same thing just happened to me and I’m so distraught. I saved my points for years for my Turkish business flights. No where did they indicate a cabin change I never would have made the change had I known I was going to be downgraded. Spent 20 minutes with a rep on the phone and he said there’s nothing he could do, I would just have to fill out a feedback form. I am also waiting on a phone call from a supervisor that I’m sure will never come. I’m currently on vacation so this was an expensive phone call and I’m just so upset.