Campanda interview questions

First I had a phone interview, then I was invited to a personal interview with four employers. Although they suggested the time and date of the appointment, one of them couldn't be there. Therefore, I later on a second round with the missing person. After succeeding with the third interview, I was invited for a "trial day" (for free, of course). After almost three weeks of that appointment, they sent me an email and said that they will give me feedback within a week. Ten days later I contacted them, as they didn't give me any feedback as promised. Just then, they rejected my application for the position without even explaining why I was not selected. Very unprofessional.