Complex sentence: UGC conducts NET exams for the appointments of teachers in colleges and universities, nevertheless, the NET has been exempted those having MPhil degree, they can teach at graduation level and PhD holders can teach at Post Graduation level since June 2006.
Split into simpler sentences: UGC conducts NET exams for the appointments of teachers in colleges and universities, nevertheless, some years back the NET had been exempted those having MPhil degree to teach at graduation level. However, PhD holders can teach at Post Graduation level since June 2006.