I’m not quite sure what your setup is, but I assume that you network model runs in some kind of server.
The easiest ways is to expose your model via adding an API layer. In Python, this is relatively easy to with Flask or Falcon. The goal is that you then have API endpoints to which your mobile app can send requests and get results. For example, an endpoint might look like
https://myserver.com/chatbot/v1/response/

Which accepts POST requests with a text as parameter. The response will be the chatbots reply which is sent back to your mobile app.
Best have a look into REST APIs, and Falcon and/or Flask to get the basic idea. I’ve done exactly this setup for an app of mine, and it’s pretty straightforward.