Iberia Airlines - Silence

My son's luggage went missing off a flight from Madrid to Split on the 8th of August. He therefore arrived for a 2-week holiday in Croatia with only the clothes on his back. We reported the bag missing at the airport. During the holiday, we called the number given to us many times but got no further info. On returning back to JHB, I logged two complaints on their website. No response. I eventually called their JHB office where I was told to fill in more forms sent to me, which I did. I followed up a few weeks later and was asked to provide more info and documents which I did. In little over a week, it will be two months since this bag went missing and Iberia is yet to do anything about compensating me for this. This kind of customer service is not acceptable.