I need to get something straight.Did u enter d N20k at once or did u enter 10k twice?If u entered it once,there is no reason for d machine to dispense just half of it,so i guess u entered 10k twice. This error occurs at times on ATMs as a result of link downtime/network failure.Just like when u try to make calls on ur GSM phone and it doesn't go thru or if ur text is not delivered and u are charged for it.(It has happened to me before) Just go to the nearest branch of ur bank to lodge a complaint and it will be corrected. Please let's not discourage ourselves from the use of ATM. I think it has more advantages than disadvantages.