If you want to change the payment method of your Pro subscription, you can update your payment details at any point of using the subscription.
Changing the payment method used for a Pro subscription
Open the Settings of your site and navigate to the Subscription tab:

Click on Update payment method:

In the pop-up window you can either add a new payment method or edit the existing one:

Tip: check the article Setting up the backup payment method if you want to enter additional payment details for your subscription.
Choose the existing payment method and click on Edit your payment method in the new window:

Then, choose your payment method (Credit Card or PayPal), enter the new payment details and hit Update:

Done! This payment method will be used for the next renewal of your Pro subscription.
Changing the payment method used for a Pro subscription
Open the Settings of your site and navigate to the Subscription tab:

Click on Update payment method:

In the pop-up window you can either add a new payment method or edit the existing one:

Tip: check the article Setting up the backup payment method if you want to enter additional payment details for your subscription.
Choose the existing payment method and click on Edit your payment method in the new window:

Then, choose your payment method (Credit Card or PayPal), enter the new payment details and hit Update:

Done! This payment method will be used for the next renewal of your Pro subscription.