Defining a usage based billing model for IoT?

i want to create a usage based billing model for IoT system.
my system is calculate number of device call, i want to send number of device call to billrun every one hour and create bill for that.
i dont know which one to use? prepaid or postpaid?
and i dont know how create input processor for API call for this type of model?

what can i do?
thank you.


Prepaid is used for cases when the subscriber is paying in advance, and need to cut his service in realtime when the quota finished. In addition, for prepaid subscriber there is no monthly cycle.
Postpaid is mainly for monthly subscription and usages can be added. You can also cut the service by using balance quota limits.


so how can i define prepaid plan with custom payment amount for each subscriber?
i have a SaaS application that use pay as you go billing model and no limitation for amount of pay. how can i implement this type of billing in billrun?