Help with reporting

[Termostatti]

I recently played game against 3 guys (or 1) who played clearly together, it doesnt let me report them, saying it was their first game, it wasnt, they are all over 300 rating, accounts made on same day. They used the dragon to help eachother out, eating meeps that werent good for them, passing the ones that helped them. Those accounts are all 3 made on same day (1 is made one day after two) checking their game history, mostly 4 player games, and all 3 of them on those games, having 1 random each game. It seems its kingsmaking all day, but i cant report em. I can only put "personal note".

How should I proceed? How to contact GM to check their history?

Names of those players Zigzag968, KUKZER and Rosario28.

Thanks in advance.