Microsoft Bot Framework is one of the best-known platforms to create Conversational AIs. By default, you will use Microsoft Luis as NLP. But as with Cognigy.AI, you are pretty flexible when it comes to integrating with existing systems like other NLPs.
Notice that Microsoft Bot Framework doesn't contain a graphical conversation editor, so setting up and running a Conversational AI has to be handled by developers or users with a lot of technical background.