Which is the correct way to customize an existing channel?

Hi, you can write a custom channel connector using the original one as a template. Just copy-paste the contents of rasa\core\channels\telegram.py in a separate file, e.g. custom_channel.py, and do the necessary customizing as required. Give your custom channel a name, e.g. MyIo, by editing the class method name. Now in the credentials.yml file, just declare you own custom channel like so:

  access_token: "490161424:AAGlRxinBRtKGb21_rlOEMtDFZMXBl6EC0o"
  verify: "your_bot"
  webhook_url: "https://your_url.com/webhooks/MyIo/webhook"

And, that’s it! It should work fine.