I hope you didn't invest too much in these so-called cloud-mining schemes. They are mostly (99.999%) scams- please let me know if you come across one that is not.
Just my opinion, if there is an option to withdraw your fund, please try to do so before the site go MIA. Stop waiting for the "friendly customer service" to get back to you.
Yes, most of them are ponzis ( like Hashocean, Bitsrapid etc. ). I am also very cautious with them. I deposited a really small amount in bw.com just to compare the profits to Hashnest ( operated by Bitmain - this is the only CM provider I trust right now ), before I move in with bigger funds. I don't think BW.com is a scam, it just has crappy customer support.