Refund adjusted against tax credit mismatch

I HAVE REFUND OF 20000 IN THE AY-2014-15 WHICH HAS NOT BEEN REFUNDED BUT ADJUSTED AGAINST A TAX DEMAND PAYABLE FOR AY- 2011-12 WHICH IS ALREADY PAID AND CREDIT IS SHOWN IN FORM 26 AS. SO HOW CAN I TAKE THE REFUND.