Submitted gstr 3b wrongly for july 2017

I had submitted gstr 3b wrongly for the month of July 2017.

I had wrongly posted the purchases for tax credit in Inward supplies for reverse charges resulting in doubling up the tax computation where as that should have been in Input taxes.

having submitted that I have not filed for July as the tax computation is beyond my abilities to pay.

I brought this issue to gst help in vain electronically to help desk and as well to GST Help center in Thanjavur.

How do i rectify the same?