The term chatbot contains multiple meanings and technological aspects. A chatbot can be built on top of Facebook Messenger or, for example, be a customised solution to fit the needs of a large company.
Find out from the supplier of the chatbot what technical platform is their solution built on. Is the chatbot developed by the company itself or do they perhaps sell a system developed by someone else? If the system or part of it is developed by another party, which areas do they deliver themselves and which come through partners?