I made a payment using PayPal Credit, but it is showing it was paid using regular PayPal- the payment is now due. Is it possible to switch this transaction to PayPal Credit?
No, not post payment. You'll just have to contact merchant to cancel order and issue a refund and try to make the purchase again. A word of warning though, PayPal reserves the right to restrict use of credit line depending on the circumstances of your purchase so there is no guarantee it will go through on PayPal Credit if you tried again.
