mistake in Gstr 3b

I have proprietorship, i filed monthly Gstr 3b and I had prepared two sales bill 1. Nov 2017 and 2. April 2018 two sales bills customer name and Gstr no. is different, we have checked Gst portal, credit goes wrong person, what to do now, we have know the same mistake before two days and tomorrow is the last day of Gstr 3b