Call us at either: +1 (646) 760-8876 or +86 (010) 5315-7551. These phone numbers both ring the other one, so this will ensure someone picks up at any hour of the day.
Alternatively, there should be a chat bubble in the lower right corner. Using that will send a company-wide notification.
Finally, we have a company-wide email email@example.com which can be used for time-sensitive matters.