Gauhati University — Refund of Certificate short payment fee which was done through SBI collect

I have made a certificate short payment of Rs 90, for obtaining my original pass certificate of B.A.LL.B.honours. There after visiting the Administrative building of Gauhati University, I came to know the actual amount is Rs 830. Initially i acquired my provisional pass certificate by paying the amount of Rs 740. Therefore, i was of the view that paying the remaining 90 rs would get me the original certificate and then I was told to make a payment of 830 in order to acquire it, which is fine. I agree to pay but since I made a sbi collect certificate short payment fees i.e.of Rs 90, i opted for refund for the same but the staffs refused. So, my request is to kindly refund the amount of Rs 90 so that I can freshly apply for my original pass certificate. Even though Rs 90 might seem to be a very small amount but that doesnot me less entitled for the refund.