Why Paypal repeatedly charges me by the debit card instead of a credit card on file?

[caseyx]

My credit card, as one of the payment options, is set as a preferred payment.  However, paypal keeps charging me on a debit card.   How could that be?  Please help.

Casey

[DPCreations]

It may be that it's the least costly option for PayPal to use.  PayPal does have the authority to adjust payment sources.