How to un charge the resource against a Work Order

Hi All,

A Resource is charged  wrongly by the end users i.e. 5 hours against a work order. Now I want to un charge the resource from work order, how to do this.

I've performed the following, kindly guide me if correct (for un charging the resource)

1) Remove the instance from the operations (successfully did)

2) Delete the resource from operation (unable to delete the resource from operation with the following error message)

Kindly help me how to un charge or remove the resource from the operation or delete the operations from work order.

Regards,

Atta