The Hilton primary contact info on Christopher Elliott's Company Contacts page works if the front line reps are grossly mishandling an issue. After writing to them about a totally irrelevant form reply and a unresolved 3 week wait to fix a stay with missing base + bonus points, I had a manager calling, a successful resolution, and 20k points for compensation.

Calling may also be better than e-mail. The fact that Hilton brands their e-mail staff as "coordinators" leads me to assume they have limited power and just push issues to other departments who actually do the work. A few times I've had one of their e-mail "coordinators" telling me to call for further assistance.