Interest under sec 220(2) for delayed demands

if the demand is genuine then pay online under head 400. Self Assesment Tax after Demand.

Then go to efiling and rectify the return and in tax credit mismatch fill this challan in Advtax/SA . 

If the demand is wrong they will reprocess and refund the excess.

You should study 143(1) of respective years and see whether they have made any apparent mistake. If they have made a mistake you should point the reason and ask for reprocessing the case.