This web site declared that for every transaction received will send back the doubled amount of BTC. I have sent 0.1 BTC and received NOTHING. Moreover the website chat is disabled and there is no way to contact them. This was advertised as] We believe that Blockchain and BTC coin will make the world more fair. To speed up the process of cryptocurrency mass adoption, We decided to run 5.000 BTC giveaway. To participate you just need to send from 0.05 BTC to 20 BTC to the contribution address and we will immediately send you back 0.1 BTC to 40 BTC (x2 back) to the address you sent it from

they wanted people to send bitcoin to this address via this website: https://www.ms-give.net/btcgive.html. the minimum was 0.05 BTC which was roughly $1900. I sent it but their chat disappeared afterwards.