Who do you call with questions about final LES?

I retired (not DRP) in October. The final LES was in November. I'm confused bc it seems to have the annual leave payout and back pay and two weeks pay and a whole lot of deductions. Gross was over $10,000 and net after deductions was under $30. lol. There was another random payment of a few thousand dollars but it doesn't match what I calculated for back pay or annual leave. I just would like someone to explain it to me. Math is a problem for me. If you had questions about an LES, who did you call?