I flew from Egypt to Istanbul in transit to Germany. I was not allowed to board the flight to Germany, the stated reason being that I didn't have the correct visa from the German Consulate. They told me I could go to Italy so I planned to fly to Italy and, from there, go on to Germany.
I texted Turkish Airlines to tell them that this wasn't fair, and that I was losing all the money I paid for the flight to Germany. They replied that it wasn't the airline's mistake that I was late arriving for the security checks at the airport in Istanbul and I missed the flight.
How can I prove that I was there and was not late?