Shocking customer service at Qatar

I had paid for my client to fly business class as he had to operate when he returned to his home country. He wanted to fly Emirates but I assured him that Qatar was the best. When he got to the airport he was downgraded to economy and promised a flight replacement. When he communicated on email to them they offered a dismal US125 when he knew another passenger received US1000 and a flight. He queried this and hasn't had a response since. Myself and my travel agent has emailed multiple times over the last two months, called and submitted queries via their website without a response or further answers. Customer Service has been extremely poor and we are still no further with resolving this case.