How to cancel a transaction?

Please, there is nothing particularly wrong with the transaction itself, but there is a scammer who keeps sending me stubborn messages, trying to convince me to send more then was dealt, and making threats. I don’t want to give my personal info to this kind.

Hey, start a mediation right away by clicking CTRL + O or CMD + O. Explain the situation to the mediator. If he is trying to scam you, you should probably receive his security deposit and the trade will be cancelled.