In your case for that TDS return there is posibilty that wrong PAN no is entered, so department has calculated TDS @ 20% on invalid PAN No.
first you should login to tin-nsdl by using TAN no. and then you should check for default status, in default status you will get the respective F.Y. and quarter in which return processing default is notified by department. then apply for TDS consolidated file for that Quarter, tha file can be send to u at your registered email id or you can download it from downloads option in your TAN account. then make necessry correction in consolidated file and file your TDS return.