Nikon Service

Bought a camera (D7200) from Nikon. Focus problems from the beginning. Took the camera back in September for callibration. Problem still there. Done extra courses (although experienced with cameras) and was fully booked (Nikon had no loan body). Took the camera back in December. Still same problem. Sent RAW etc. Never bothered to reply. A Nikon pro tested and said immediately there is a focus problem. Camera went back in April. After Raws was sent and Nikon confirmed back focus issues. Camera came back - still no sharp image. Phoned Nikon numerous times. Sent RAWS again. The head of service confirmed the focus issue. Now they want to sent a demo (when one is available) and look at the camera again. WHY???? They have done it numerous times and they haven't been able to correct this. So my question is why sent it back again with no service being delivered.