I will change the address on cex.io to this one "1HdK3k1LWG429jADbu9GXTszWmGGz9uVdX" will provide a screenshot of my wallet and cex.io and sign it with that message.
AFAIK cex.io does not allow you to sign messages. Did you ever use a programm as wellet and posted an address that is controlled by that wallet?