Chaudhary Charan Singh University [CCSU] — transaction error & amount deducted

Address:

Meerut, Uttar Pradesh, 250002

I filled my examination form and i was on the last step to pay the fees of my examination form. i paid the fees then suddenly it shows that the transaction is unsuccesfull but the amount of fees is deducted from my account. so, please help me how can i refund it. And my second complain is that when i tried again for payment it says :- SORRY!
We were unable to process your payment
Error Reason
This txnid has been used previously or was successfully captured.

Corrective Action
Please re-attempt using a new txnid which hasn't been captured. Please note that the txnid value must be unique for every new request to PayU. In case a txnid has been captured previously, it can't be used again and hence throws the above error.
So please tell me the solution for these 2 problems.