In that recent interview, Huobi's CEO said that they have 20 people on customer assistance.

I see that their phone numbers have a '4000' prefix.  Could that be paid service in China?  Could that be how they make money? 

400 toll-free numbers with prefix "4001" are international toll-free numbers which can be routed to destination numbers inside or outside of China. 400 toll-free numbers with prefix "4000", "4006", "4007" or "4008" are national toll-free numbers which can be routed to China destination numbers only.