If you're a diamond member, the Diamond Desk is generally a good outlet (although their main MO is to phone the hotel's GM and say that an important customer had XYZ problem). Otherwise, I would write/fax the hotel (or speak to the duty manager if you're still there; it wasn't entirely clear from the post).

Depending on the particular experience, possible compensation other than money off the bill includes HHonors points or a "be my guest" certificate (free night).