Urgent - VAT Turnover Shown as GST Turnover and Tax paid in GST Return 2017 - 2018

I am doing Contract Work While Filing GSTR - 3B & GSTR - 1 For the year 2017 - 2018  i have show VAT turnover Rs. 9029473/- Amount as GST turnover and paid tax Rs. 487724 along with Interest on May 2018 only department give the details that the turnover is VAT and they have deducted 2% VAT only now i am unable to reverse the GSTR - 1 and GSTR - 3B i have all the GSTR - 3B & GSTR -1 Till September 2018 in October 2018 GSTR - 3B i want to pay tax how can i adjust the above tax paid in GSTR - 1 & GSTR - 3B no reversal for 2017 -2018 in GSTR -1 time barred  kindly help to adjust the amount in GSTR - 3B & GSTR - 1