If you have received a customer notice saying 'This payment cannot be amended or cancelled as the original payee details are not available.' then it normally means that the scheduled payment you are trying to amend or cancel no longer matches the original payee details used to make the payment.
If you have recently removed or changed the payee details, you can gain access to the scheduled payment by re-adding or reverting the payee details back to their original state. The payee name, account number and sort code must match the original payee details used when you set up the payment. This will allow you to amend or cancel the scheduled payment.
You can then remove or change the payee again however we would recommend waiting until the scheduled payment has left your account, since you will experience the same situation, should you wish to amend or cancel the scheduled payment again.