How to stop automatically Billing in Heroku website?
If you're still on free tier, it will not charge you. When I upgraded to hobby, I was only charged for how often the service was used (often less than $7). They were very honest - I have had no problems with Heroku. If you elaborate on your concerns, maybe I can provide a more tailored response.
You can stop charging at any time. If you're looking for specific information on how to remove your card/billing information, thus reducing down to the free tier you can change your dyno type in "Resources" on the Heroku web app.
I am kind of scared of filling billing information on the Heroku website because of the automatic billing option in case I forget to remove an account.
Help me with your experience.