While you cannot change the payment amount or bank account for a single payment in an AutoPay series, you can cancel a single automatic payment and make a one-time payment in its place. To do this, sign in to your account online and click on 'Pay Bill' in the top menu bar. Pending payments will be displayed at the top of the screen. Click 'Cancel' next to the payment you would like to cancel. Now you can return to Pay Bill and select either Standard Payment or Express Payment to make a one-time payment in place of the canceled automatic payment. No change will be made to the rest of your AutoPay series.
Note: Any payment with a Processing status cannot be canceled.