Quick questions about billing and messages : 1.Is it really counted based on the amount of messages? If so is it costing money for 1 message each, or for a bundle of messages (like 5000) 2.Is it safe (like if a user just wants to drain your money, could he/she just sends tons of messages and it would work? Or is there a protection against this kind of user/act)? 3.Is there a reset of messages usage each X time ? 4. Are messages coming from the chatbot counting in the message usage ?