Fake volume is something you can see on most centralized exchanges and if you send them your coins they are not yours anymore.
I never used Mercatox exchange but it does not look reliable and after reading what you posted it appears they have very bad support.
Maybe you can try contact them in public on their social media accounts like twitter @Mercatox_info or in telegram @mercatox_official
Contacted via Twitter, no reply yet. Their TG is just a channel. Last 1 month i am trying. Sometime they forward support ticket to their Finance department sometimes to Security departments, but last 1 month, i can not make withdraw of my 11.63 ETH from that Mercatox.They kept my account locked.
That's one bad exchange down I used to trade here two or three years ago my transactions are all good, they are still good but after reading reports like this, you come to think that these old exchanges are losing in the competition from new players in the industry, it's time to re check if these old exchanges are still worth trading, if they are not on the top 10 better think twice trading there.