what makes you think they were boosting? beachhead has already said there were several clans that broke the 1000 cp mark this clan war. The scoring system allowed for some high scores across the board . You can report clans via twitter beachhead they say that they investigate every report.
correction, several clans boosted to obtain 1000 points to get the special patch. was there clans breaking 1000 points in earlier clan wars?
while you may be correct that clans did boost to get there . In this clan wars they did state that several clans broke the 1000 cp without boosting. The scoring system this time favored higher scores. The emblem your referring to was for 1000 cp collectively you did not have to earn it in a single clan war . I can't answer for previous clan wars as far as clans reaching over 1000 cp in a single cw , I just know that they said it this time as I went to the twitter page and read it yesterday .... Either way your original question was where to report a suspected clan of cheating and beachheads twitter is where to do it . I also read there that they investigate every report of cheating that they get there.