A customer pays a bill this morning (not preauthorized or recurring). Later in day calls and wants to cancel the transaction. If the bank fails to process the cancellation on time or the info input is incorrect resulting the payment being processed would this a reg e covered error.

It depends. What form would the bill payment take? ACH? Check drawn on the customer's account? Check on an account of the bank (or third party) with e-debit to customer's account to pay for it?