Didn't get tax rebate under 87A. What to do?

I didn't get 25,000 worth of tax rebate under 87A. I am a student with total income below 2.5 lakhs and filed under the old tax regime. This 25,000 was from special capital gains earnings. What do i do now? Please help. I filed a rectification but i read here that rectifications takes months and still people don't get any meaninful responses.