Chatbot learning recommendations?

Want to create a chatbot.

Saw the option of Google Dialogflow however – I dont want to put a payment plan.

So… any recommendations of how to learn how to create a chatbot where I don’t really have to key in any kind of payment options?

Any source material that shows how to create one where I can create one concurrently would be great! Especially if I don’t have to pay for any software where I create the chatbot in.