Prepaid/postpaid

I’m using free version account and I don’t have plan of purchasing any function pack. I have gone through the functional limits and I’m ok with that. I just want to know, everything is prepaid or not.?
If I don’t purchase any function pack even once (so that I won’t click a option like auto purchase) , Is there any chance that I get a bill unexpectedly?

No, there is no chance of that, Backendless does not charge you anything without obtaining your consent.

Thank you so much.