This article will explain how your customers can update their card details themselves within their own account.

From the main storefront page, they can select Sign in, and once logged in, they can choose the View payment details button, as shown below.

They then can select "Add payment method" to enter the new card details, as shown below.

They will then be presented with the screen below, where their details can be entered and added. This will make the new card the default payment card for future payments.