Tax deducted twice from refund against same demand order

I have a client who has filed his return by himself for the PY 2020-2021 , he missed PGBP income in his original return (filed for refund of rs 22000) and filed a revised income (filed for refund of rs4000) in this regard. but he received refund due from original return i.e rs 22000. later he received a demand order for rs18000- which he paid through bank (offline).I filed the return for the PY 2021-22 (refund 32000), but the amount of Rs.18000 was deducted again from the refund against demand order and only 14000 was refunded. In this regard , I did seek advise from Income tax through grievance, they asked me to rectify return using the payment made against demand order for PY 2020-21 . But the rectification order came as the refund is adjusted against the same demand order. What should I do - the tax was deducted twice in PY 2020-21 & PY 2021-22