Accept test payments on prod app

[pawel_experify]

Hi,
We have problem with approving our application. We are using latest remix-app-template, for checking current active subscriptions we are using https://shopify.dev/docs/api/shopify-app-remix/v2/apis/billing#billing-propertydetail-check

await billing.check({
    plans: [MONTHLY_PLAN],
    isTest: false,
  });

that's how our code on prod looks like, but our submission is rejected because they cannot change pricing Plan. The reason of that is that they use test payments (even though we require not test payment during init of charge process), and we do not accept test payments on prod version (isTest: false).

So my questions:
1. Should I set isTest: true on prod version?
2. If yes, then how I can know that payment is "test" since webhook APP_SUBSCRIPTIONS_UPDATE does not provide any informations regarding type of payment (test or real)
3. Or I should just use isTest:true on prod and that's it?