Letter of Credit Forum

Hi to all! Having received an order from a customer, an irrevocable L/C was opened from his side. After the shipment the bank returns an MT734 swift denial message due to discrepancies in the invoice and the packing list...not in the amounts but the headers on the invoice were on greek language where these on PL where on english. In the denial message the bank states that if the customer sends a swift that agrees , the bank will proceed in the payment. However the bank sends us a swift suggesting to send 10000 euro less since the customer wants a credit note for n older order. In the past, in similar situations, we paid 70 euro penalty and thd money were released. my question is what happens in these cases? Can anyone for a comma or a small discrepancy deny the payment?Thank you in advance !