How do I change my payment method?

Open You → Subscription and use the payment-management route for the service that bills you. A web purchase is managed through web billing. An App Store or Google Play purchase uses that store's payment settings. Changing a card elsewhere does not update the existing subscription.

Check the next-payment information after the change. A payment-method change is separate from changing your Calsa plan or billing period, which has its own effective date and confirmation. If renewal already failed, also check that the billing service recognises the updated method.