Rectification u/s 154

for assessment year 2006-07 I have claimed deduction u/s 80-dd of rs. 50000/- instead of 80-u now I have received a notice disallowing of the deduction u/s 80-dd and demanding tax upon it . now i want to reply to the income tax authorities and similaraly I want to claim the deduction u/s 80u if some one has any experiance regarding this querry pls reply soon