patch https://restapi.ordergroove.com/subscriptions//upgrade_to_prepaid/
This endpoint will allow you to upgrade a pay-as-you-go subscription to a prepaid subscription
Authentication
Validation
This operation can only be called on subscriptions that are associated with a product that is prepaid eligible. Attempting to call this mutation on a subscription that is not associated with a prepaid-eligible product will result in a 400.
Side-Effects
After upgrade, the prepaid subscription will have 0 orders remaining. As a result, the customer will be charged to “renew” the prepaid subscription at the time of their next order being placed. This allows this upgrade flow to be called directly from the customer SMI without granting the customer free fulfillments they have not yet paid for.