The lesson of losing 350u has exposed the scam of first paying and then paying, or offline cash transactions.
There is a scam on the Internet that charges a high price first and then pays the user. Let me reveal the secret to all the novice friends. First, the scammers will advertise through various Twitter software, telling you that they accept U and the price is extremely high, and they support payment first and U later, cash transactions, etc. When you contact them, your U is ready to be cheated away by them. First, the scammer will ask you to buy B from the trading platform, and then ask you to withdraw cash to your private wallet. (The wallet here may be Euro-Yi's WB3, Coinbase Wallet), then the scammer will ask you to try a small amount, such as 10U 20U, and then ask you to exchange once on the grounds of currency anti-tracing. After the exchange is completed, a screenshot will be sent to you. At this time, a high-imitation currency will appear under your wallet, which may be USDC, Japanese Yen, Bitcoin, etc., which are actually fake contract currencies. You believe the scammer's words and exchange, take a screenshot and send it to the scammer, and then he will transfer money to you.