Can the website process prepaid credit cards?

As long as your payment gateway is configured to accept them, they should work. If you are seeing declines, we would recommend reaching out to your payment gateway. Commerce7 simply passes the credit card and payment information entered and waits for your gateway to respond with Approve or Decline. It's possible that they are being declined in your gateway because it's a pre-paid card or other decline reasons. Your gateway should be able to provide a concrete explanation for the declines.