SME: 'Due date of sight bill should be counted from date of presentation'

What a firm seeking supplies from abroad on credit should do in case there is an error in the contractual documents

Q. We had contracted with an overseas party for supply of certain goods on 90 days’ credit. By mistake, he sent the documents payable at sight through banking channels on collection basis. Later, he arranged with his bank (the remitting bank) to send a SWIFT-authenticated message to our bank (the collecting bank), changing the tenure to 90 days. Can our bank act on such an instruction or ask for a bill of exchange at 90 days’ sight, and if our customer does send such a bill of exchange through his bank, will the due date be 90 days from the