Inform railways regarding your this transction no. Also inform citibank about
this transction no & send printout of the page saying transaction not successful
showing "failed payment".
Get reply from them. This will work as an acknowledgement of the letter you send
them saying "payment failed".
Normaly it takes 15 to 20 days for reverting the amount. Citibank is responsible
for this . You have to prove "payment failed".