Is it possible to change a customer’s payment method from PayPal to Credit Card?

PayPal billing agreements can be changed over to credit card fairly easily. There are two ways currently to handle this. If you're an admin user, you can head over to the customer's account page from within the app, then click on Edit near their Billing Information section, from the following page you should see a red Clear Billing Info button in the top right-hand corner of the page which will then remove the information and allow a credit card to be entered.

If you simply want to change the information over to a credit card, you could access the customer's hosted account management page instead. From the customer's account, you'll want to scroll down to the Hosted Pages section located just beneath the Billing Information. As long as the hosted pages are enabled and the customer view in the hosted page settings has been set to Account Login, you should see a URL labeled as Account Management URL. You'll want to visit that page specifically and from there you should see a button showing as "Need To Change Payment Method?" simply click on that, then select Credit Card, and you'll be able to make the change.

Please note that the Hosted Account Management URL is a customer facing page as well, so you can always send the customer that link directly and allow them to make the change and add the credit card details as well.