Rectification u/s 154

My friend's income is little above 50 lacs. Hence we considered the 'Marginal Relief' and paid taxes accordingly. Later on, he received demand orders from CPC without considering Marginal Relief. We have filed rectification request u/s 154 twice, but every-time we get the same demand again.

There is no error in calculation at our end. What can be done further to nullify the demand as it is incorrect.