Duplicated Booking??

We were denied boarding our plane in Athens on 16/07/2023 for our return journey to Cape Town. We were told that our names did not appear on the flight even though we had tickets. The system claimed that there was a duplicated booking? We had to sleep in the airport, and had to book new tickets to get home. There was no Ethiopian airline support at the airport. We incurred tremendous extra costs for the one-way tickets home. I would like to be re-imbursed for these tickets, but get no reply from Ethiopian Air!