‘My son is buying crypto by giving money to trader he met on Instagram’

Q My son recently started his first job and says he is now “investing” in cryptocurrency. He’s been talking to a crypto trader who contacted him on Instagram and has paid €250 into an account. He thought this money was his to start trading with. As it turned out, the €250 was just a joining fee to get into a Telegram group, and he needs to deposit more money into this account to actually start trading. The trader recommended adding between €250 to €500 to his account to start with. I’m very sceptical. Is there a way to check if this trader is legitimate?