Discrepancy in 3rd Economic Impact Payment

There is a discrepancy between what the IRS says we received as Economic Impact Payment #3 (EIP3) on Letter 6475 ($3,500; married filing jointly with 4 dependents) and what was actually direct-deposited into our bank account by US Treasury for EIP3 ($258.58).  Has anyone else run into this problem?  I've tried calling the IRS and can't get through to talk to a live person.  All of their automated help is useless.  Any advice??