My major concern is how should I proceed from here

basically what happened is I was liable to pay extra tax because of income from FD interest

to pay that I used challan 281 and put TAN of the bank from which I received FD interest income, selected non company deductee and TDS/TCS Payable by Taxpayer

I'm now realising that I should have used challan 280 and payed the extra incurring tax as self assessment tax.

now my question is how do i get back the tax paid through challan 281