I'd like to hear from you about what i have found out.
In our place they open a company who will accept investments which they guaranteed 400% interest for 1 month. I have found out that they do crypto trading. Is this usual to identify them as a scam?
In my experience yes, because those who promise a 400% return in just a short period of time is totally too good to be true so be careful. OP it looks like a signal group where they encourage newbies to join with them and scam them later on, phone calls is very rare form of scam. If you want to help newbies on trading or anyone then try not to ask for money or teach them how to use indicators and not how to listen to your signal.