I agree with Trevor as I played in all of those closed games at UA.
My solution if I know its blatant: call myself out, pull my rag and put my gun up. I then walk over to where the guy is I know who is cheating and KINDLY ask for his name. If I get it, I inform game control. If I don't, well, taking the time to walk up and ask has allowed me to get a good idea of what he looks like so I can report it to game control anyways. The key with that solution is being calm and not losing your shit on the person. Simply ID the person and walk away.
Some people have gotten defensive when I have asked for their name and I simply ask for it again, calmly. If they absolutely refuse, again, I have now visually IDed the person so I then go to game control and explain what has happened. Generally works most of the time and by being cool and collected you are giving no bait for conflict.
Guardians of Asgaard
NO EGO, ONLY HARD WORK
Primary - Z-Custom VFC ZTW
Secondary - KWA ATP