You should have a support email, support documentation and a support process setup on your platform and website so that Customers can get in touch with you in case they need to update their Credit Card details. 

If the payment was processed using stripe then follow the process outlined below.

If the payment was processed with Paypal then you can instruct your customer to independently update his Credit Card or add a Credit Card following this process.

How do i change my Creditcard info on my Paypal Account

Tu update a Credit Card or add a new Credit Card when a customers' payment was processed using Stripe.

1.: Go to your stripe dashboard 

2.: Go to Customers and search for the customer. 

3.: Click on Add Card and enter the card details the customer has given you.

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