Gst return query

Hi,

I file my Gst returns through Cleartax and they are integrated with all the e-commerce platforms. So they are uploaded invoice wise on the Cleartax platform and the time of filing the return Cleartax compiles all the invoices and credit notes etc. and fill it automatically for us.

I have not shown a sale(B2C) for the month of Sept 2018 and have filed Gstr 3b and Gstr 1 of that month.

Please suggest a way by which this mistake can be rectified either manually(GSTN) or thru Cleartax.