I have a question regarding payment for my SAAS app using Shopify GraphQL billing API. I am unclear about payment process if one store owner try to update subscription of my SAAS app which is initially subscribed using some other Shopify store.
Sam installed my SAAS app in his Shopify store. He registered on my app and choose to get a subscription and pay using Shopify billing. After choosing subscription Sam is redirected to Shopify payment page where amount is paid. After payment Sam is redirected back to my app and get access to features (All good).
During registration process I also save Sam's store information at my end (e.g store name, store domain, token etc).
After installation, As Sam is already subscribed and made payment using his Shopify store. So, when Sam again opens my app from Shopify he will be automatically logged in using Shopify store information. If he clicks on logout it will be redirected to login page. where he use email/password to logIn again.
On the other hand John also installed my app and did same. Subscribed to my app and made payment from his own store.
The problem is that if Sam logs out his account and logs in again using John's email/password and try to update subscription. Here my app will take user to logIn on John's Shopify Store for billing So the payment can be completed from John's store.
Here Shopify app reviewer asked me to use the same store for billing also (i.e Sam's Shopify store).
My question is that how can I use one Shopify store to update a subscription of my app which is initially subscribed to some other Shopify store and payment is being made on monthly basis?