I've tried through Email, Chat, this community and finally through Phone. 

There is no way to receive an answer. 

Email = over a week and no answer
Chat = not available
Community = no answer at all

Telephone = after clicking myself through the callcenter -> I get a message "no support available" and they hang up 

I haven't experienced that yet with Zoho to this extent. This is incredibly frustrating considering how buggy the new Zoho One UI is.