Demand notice received

Hello.

In response to notification of high value transactions(Bank FD & Saving a/c Interest income), I paid self assessment tax against same, revised my ITR and filed it on the very last due date i.e 31st Mar.

However, today, I have received a demand notice seeking the same amount(around 200 Rs higher though). Interestingly, this is mentioned under Advance tax. head with reason highlighted as : Challan is not available for the AY. I have the challan receipt and the AY is correct as well: 2020-21.

I believe I should have filed tax under Advance tax head instead of self assessment. Can someone confirm this? If so, how can this be rectified? 

Thanks.

EDIT : I have also noticed that the Form 26 AS doesn't reflect the Challan details as of now.