How can I manage downgrading from a paid to a free plan in my app?

[thevoiager]

Hi!

I'm building an app with 2 plans: a free plan and one recurring paid ones. 
I have a question: how I can manage the downgrade from Paid to Free plan?

I've set API integration but when I try to downgrade plan from Paid to Free plan get the error "the price must be greater than zero"

Thank you!

[Subash-Ghimire]

Hello,
If you are planning to give free plan while downgrading then we can remove the implementation recurring charge API endpoint to be triggered once click on free plan.
Case 1.(For recurring charge)
Once user install the app from Shopify app section, user will be redirect to plan approval page. Here you need to implement the billing model for recurring charge.
Case 2. (Free plan)
Once user click on downgrade action, you can identified that user as a free plan and remove the implementation of  recurring charges billing API.
This way your app won't be creating any charge associated with that user. Hence user will be able to use your app on Free plan until upgrades to paid plan.

Thanks!