Royal Playboy
If its your cable under your name, change password for buying pay perview or call cable company and block it for good
On my system (satellite) you have to order permanent program changes (vs. pay per view movies) by phone or over a website … not using the cable box. But even if you could tell which box, does that “prove” who ordered it?
Seems to me you need to cancel the order and get a note on your file that you are the only one allowed to make programming changes. Whether you do it via password or some manual mechanism … like talking to a cable representative … is up to you.
In the meantime you may wish to have a talk with the members of your household an, depending on how strongly you feel about this, just tell them it’s unacceptable or be punative (e.g. threaten to take the cost off all allowances or whatever unless the guilty party owns up).

“Someone in the house ordered playboy on demand, is there a way i can tell which tv it was ordered from?”