If you suspect foul play at the check in counter you should contact the operating Captain after the flight and he will have the details.
Ie total pax and weight info.
Then make a report to the relevent manager in CX, he will follow it up with the "Airports dept" to see if there was any mal-practice on the day.
And copy the report to the AOA.
The outports are frequently checked by HK to see what they do in respect to downgrading/upgrading. That's why they are careful in what they do.