Yes i can sign a msg to prove that its my address but do you think that this will make any change since he is refusing to refund me or or his other players...?
Can you sign a message to prove that you own these addresses? It is clear that transactions were to secondtrade-related addresses, but that doesn't prove you own them.
you used transaction id that you selected. so we can not refund you.
EDIT: Their account has some negative trust, but I'm not sure if it is deserved.