refund of cancelled air ticket Goibibo, Air TicketS- ROUND TRIP Complaint

i booked a air ticket of go air by GO IBIBO from delhi to ranchi (17-06-12) and returning ticket from ranchi to delhi (21-06-12) these tickets was of 15759 rupees .but i cancelled a ticket of ranchi to delhi , this ticket was around 7500 so i should get refund around 6300 after the charge of cancellation but they refund only 2900 . i had complaint three time but there is no response at all and i spend around 300 rupees as phone charge to talk with the goibibo on this matter.