Demand due for income tax paid 2 years back while processing the return

I had paid INR 2800 income tax two years back in July while filing the return and also have the bank statement to prove it but there is a demand notice for this amount which has come to me now. I tried searching the epay payment history and challan but there is no record.

How should I respond to this? I agree with the demand and have already paid but somehow income tax portal has no record and is asking for a challan number. I have bank statement as the only proof.