How can i make a Feedback

How can i make a feedback in The Black Market?
I got scammed and i cant find the button to give him a bad feedback :S

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But i didnt Requested a Trade cause he PMed me and didnt write in my thread.
Im new in this Epvp trading system so i didnt knew about that.
Can you give him a bad Feedback in my Place if i give you enough proves?