Refusal to refund cancelled ticket

My husband booked a flight to Amsterdam with a stop over in London through E-bookers on British Airways. The ticket had to be cancelled prior to the flight as nobody informed him that he would require a transit visa for Heathrow. The ticket was cancelled by an agent of British Airways at the BA counter at OR Tambo Airport. The same ticket was resold to another passenger before the flight. When trying to claim a refund as the agent told him to do, he was sent backwards and forwards from one person to another. E-bookers refuse to help as they claim the ticket was a \no-show". Every time we speak to an agent from BA"