Hi Susana
You should call the Airbnb help line immediatly, they can look into the messages and see that it was the guest that wanted to cancel not you and reverse the penalties.
We had a situation where we couldnt get the guest to cancel because of a language problem and the room was not suitable for them so I canceled the booking without realising that our Super host status would be taken away for 12 months, I didnt think I could do anything about it but when we went to the Airbnb open in LA I explained everything to them, they wnet through the messages to see if it was true and reversed the penalty, they said in future alwasy call them before cancelling and they can do it for us. Hope this was helpful.
Good luck
Glenda (Australia)