Your case is an example of how scammers can easily scam crypto traders with tempting offers. Perhaps you should be asking yourself why an exchange would let you sell bitcoins at a higher price than the market price. They let you withdraw a few times to build trust in them, and to make you willing to deposit large amounts of funds. Sorry for your loss. But thank you for making this Scam accusation about this matter. This thread will alert many crypto traders who run after such tempting offers.
Actually I and one of my friend had a good experience on another exchange I dont remember which one but there a token price was UP as compared to others we found it from CoinMarketCap so we deposited and made some profit then price of token went down so that lead me to fall for this scam and yeah very dumb move, also trustpilot had some fake reviews on it and it was not flagged anywhere so I decided to post and now I know the same guy owns another exchange/website which is
https://coinwan.net/ same UI same rates and same scam but this one is flagged already.