How to add gstn number in old invoices on gst portal

How can I add GSTN number for any particular invoice of November 2017 in GST portal. I have mentioned all invoice in B2C (Others) for which I do not have GSTN numbers at the time of filing. Now customers are complaining that they are unable to see their purchase from us in thier GSTR 2A. How can i solve this issue. I have gone through GST portal but it does not allowing me to add GSTN number for the invoices which i have pur in B2C other.