If the conversation is still there, let's do the double checking again op.
1. Make sure you're in the right group which is
https://t.me/CB_coinbene (can be found in their website if you scroll all the way down)
2. Find the admin who you suspect contacted you and make sure they have the 'admin' sign next to their name otherwise they're fake (
check for an example).
-if you have telegram for mobile, searching would be easier as the app allows you to filter messages sent by a certain user (
tutorial). There's also a search bar in telegram web but I don't think it allows you to search for a certain user's messages.
3. Go to their profile and select the message symbol, and if you get the exact same convo, it means they are the same person, if not, someone was trying to impersonate the admins to scam users.