How to manage prepaid use case in Subscription Billing?

I privation to plan beneath prepaid scenarios. Please supply guidance to plan the aforesaid successful Subscription Billing.

1. Recharge Mechanism to update the Allowance successful SB - person petition from outer strategy regarding recharge
2. Once Allowance is consumed, nonstop trigger to Network constituent to degrade the net speed
3. Create the billing papers with prepaid indicator successful billing document, truthful that aforesaid won't beryllium charged again to the lawsuit successful Invoice(Invoice procreation successful income billing)

How to execute supra scenarios successful SB? Which APIs tin beryllium utilized to update the Allowance and to nonstop the update to network.

Thanks.