Luggage broken into on Ethiopian Airlines, and they just don't respond!!!!

1. On 17 April I arrived in Stockholm Arlanda airport on Ethiopian Airlines, flights ET 808 JNB to ADD, and ET714 ADD to ARN. My booking code was BRLTPP. Baggage tag number was 3071 ET861959. 2. I drove home in my hired car, and when I arrived home and opened my suitcase, I found that one of my three suitcases had been broken into. The lock had been twisted and broken off, and the suitcase zip was broken. Inside the suitcase there was a large piece of wrapping plastic, of the type that are used for wrapping suitcases for security purposes, and which did not belong to me (I had not wrapped my suitcase). This clearly indicated that the luggage had been tampered with and broken into (but nothing was ******). I can provide photos of the damaged suitcase and of the luggage tags. 3. I immediately, within hours of my arrival, reported the matter to Ethiopian Airlines call centre, on phone number +46-8- ********** , to their representative Ms Salem Mengistu. She advised me to notify Ethiopian Airlines by email, which I did immediately, on Wednesday, 17 April 2019 12:23, 4. Ethiopian Airlines representative “kidest” refuted my claim on the basis that the damage was not reported at the airport upon arrival. 5. According to EU Regulation 261/2004 if checked-in luggage is damaged on a flight to the EU, the airline is liable for compensation to an amount of approximately EUR 1 300, as long as the matter was reported within 7 days. (It does not necessarily have to be reported at the airport.) 6. So far, I have not managed to get Ethiopian Airlines to entertain the claim, and in most cases Ethiopian Airlines just does not respond to my emails.