I tried reporting a cheating channel with a clear note of why I was doing so, but I checked it again now and it's still there, having 60 members(twice of when i last checked).
Why does Telegram not take this seriously? I don't know if it makes a difference but given that codeforces is sponsored by telegram, maybe doing it should have been much easier?
Moreover I think that if this happens, it would wipe out most of the cheaters. Talking of alternatives such as WhatsApp, I don't think much people will risk their phone number exposed while being on that group. And I don't know of discord, maybe it takes reports more seriously?