i got a total outstanding demand of rs 16000 in 4 asseessment years 2007-08,2009-10.2010-11,2012-13 . i paid challan under regular assessment of rs 16000 but in the challan wrongly mentioned ay 2015-16.due to which my outstanding demand is still showing in the site. i had a refund of rs 1097 in ay 2017-18 but it got adjusted against this demand of rs 16000,which i have already paid.plz tell what to do to either get refund of rs 16000 or adjust my outstanding demand.