GoAir — rescheduled flight

I have a flight from hyderabad to delhi on september 6 morning 10:30 which has been rescheduled to same day afternoon 2:20 and they sent me an email on the same day that is 6th september morning 6:30. But i have a slot with nbe (National board of examination) in delhi from 2pm-5pm on 6th september to receive my documents. I contacted the airline helplines but they were not helpful and the worst is they cut my call and didn’t respond. I need justification. I demanded them either they provide another ticket for any other airline as reaching delhi is very important to me. But they cut my call!