Error in GSTR 3b and export refund issue

dear expert,

I have exported goods against payment of igst in December 2017.

this details should be submitted in 3.1.b in GSTR-3B but I have mistakenly submitted in 3.1.a
but igst payment is correctly debited.

but I haven't yet received refund from icegate.
custom dept saying that they have not yet recd data from GST network so they cannot proceed for refund.

GST dept saying that since amount is not recorded in 3.1.b so data cannot be transmitted to icegate.
they are saying to put the data in next 3b returns but what about the taxes I have already paid in 3.1.a.

any solution...
plz reply