Advance income tax paid is not adjusted, what should I do

I am a PSU employee. For AY 2013-14, I had paid self assessment tax( on bank intt) of Rs. 7075 online under Major head 024 & Minor head 300 in July 2012. The paid tax is reflecting in 26AS also.. I had shown the same in my return also but IT deptt has not taken it for computation & sent me a demand of Rs. 7070/-. I had filed rectification for tax mismatch but IT deptt again sent me the same demand of Rs.7075. The Major head should have been 021 inplace of 024. What should I do? Can anybody tell me detailed procedure for resolving the issue.