How to change the PayPal account that is billed for Bandcamp Pro:
Unfortunately, because of the way PayPal's recurring billing system works, it isn't actually possible to change the PayPal account you use to pay for Pro without first canceling your subscription and letting it expire. You can cancel your Pro subscription from your Profile page, and check when your subscription will expire. As soon as your subscription has expired you'll be able to sign up again with your new PayPal account. Don’t worry, all your Pro settings (custom domain, optional streaming settings, etc) will turn back on immediately, unaffected.
How to change the billing method:
If you’d like to change the card or bank account that is billed for Bandcamp Pro, please log into your PayPal account at paypal.com and change your default billing method.