Exemption s was mentioned under incorrect sections. Received U/s 143.1.a with deduction 0

I am physically handicapped person with disability of 76%. Im eligible for a tax exemption of rs 75000. I have filed my returns. I have mentioned that 75000 in section 80u.i have filed my disability exemption in 80dd for last 2 years. Also i made a couple of other mistakes i mentioned my NPS in 80c instead of 80ccd 1B and my lic in 80ccc. Due to these errors i have  received a notice 143.1.a stating my total deduction are 0 as per form 16a and not 225000 (150000+75000). I want to know why was my 75000 not considered? Is that because i filed it under 80dd previous year ? And my other 150000 was not considered because i selected incorrect sections ? Can i file a revised returns with NPS in 80ccd 1B . lic in 80c and disability under 80u ? Can someone please tell me.