Revising commercial invoice/bill of entry

I don't know if this is the right forum, but I need some help. My company sent a UPS international shipment to India (I'm from the US) earlier this month and the customer received his goods. However, he's telling me that his bill of entry is incorrect, causing a banking issue. More specifically, the value of his goods on the original bill of entry are incorrect. I'd like to deal with the issue, but I don't know how. I'm not familiar with a bill of entry. I had to search the term on Google. The only documents required when I ship internationally in the US are the commercial invoice. I'm sure some of you had to deal with bill of entry issues. What do I do? I'll contact UPS and check the process of revising a commercial invoice, but I don't know if I'm allowed at this point (considering it's already delivered) or even if the bill of entry will be updated for my customer. I looked through the bill of entry that my customer sent and saw no contact information on it. Any help?