Only had to complain once myself. Chain refusing to provide promised/required/verified at booking HH breakfast (the run down Boulders "Curio" hotel that has a flyertalk thread noting the issue. Mostly my mistake for making a reservation there in the first place. Overpriced and crummy, like a badly maintained timeshare.). Order of escalation I'd use is:
Front desk/manager
Hilton app review of stay
Hilton phone CS
Third party website reviews (TripAdvisor, etc).

For my problem, within a few hours of the in app review, received reply saying the GM would contact me/ resolve in the morning. GM did no such thing and no luck at front desk. After another in app response following checkout, GM called me a couple hours later. Offered 50k pts, I agreed. Hilton app/email followed up confirming the resolution.

Fast forward couple months, points never showed in account. Followed up and Hilton credited them manually, presumably taking the loss themselves because the property didn't pay them the points back. I followed up with third party reviews noting the repeated issues (and no follow thru / never posted promised points from the hotel).