As of May 18, 2020, the behavior of the Self Service Page has changed for sites with the Multi-Gateway feature enabled.
Customers can now choose any payment method that has a default gateway configured in Chargify, with these restrictions:
ACH conditions - see ACH Overview.
Direct Debit - it is not possible to change a payment method if there is a pending payment with Direct Debit.
In addition, payment method updates will always be directed to the default gateway for that payment type.
For example, if a customer has a credit card that is stored in Stripe, and then Braintree is added to the site and made the default gateway for credit cards, then when that customer updates their card, it will be stored in Braintree instead.
Previously, updates were directed to the same same gateway where the payment information was vaulted, and only payment types supported by that gateway would be available.