Q: I booked three nonrefundable tickets for my wife and me on United Airlines to fly from Orlando to Rome. United resold the middle seat between us on three of the five flights.

I asked for a refund, but United is telling me I can’t get my money back since I purchased nonrefundable tickets.

But how can they resell the seats I paid for? I’ve sent emails to the executive contacts for United on your website, but United won’t even give me a travel credit.

Can you help me get the $660 back I spent for the extra seat?

A: United Airlines should have kept the middle seat you paid for empty. United offers the option of buying an extra seat for the same price as your original ticket if you need more room. That obligates United to keep the seat empty.

Your case brings up a longstanding grievance. When you have a nonrefundable ticket and can’t make your flight, your airline can resell the ticket, collecting money for the same seat twice. This strikes many air travelers as unfair. Lawmakers have suggested mandating that an airline refund a ticket if it can resell the seat, but nothing has passed.

You were smart to escalate this to the executives at United. I list multiple executives on the site, and you could have been more persistent. Also, you might have considered a credit card dispute. Under the Fair Credit Billing Act, you can file a chargeback for items you paid for but didn’t receive, such as an airline seat.

So what went wrong with your ticket? I checked with United and it said the boarding pass for your extra seat wasn’t scanned when you boarded your first flight. You told me that you reached out to United the day before your flight when you had a problem checking in. The agent instructed you to deselect the extra seat when you checked in.

“The reservation was marked as a no-show by our team in Orlando, which ended up canceling the advance seating assignments,” the representative said. “That made the extra seat available for reassignment.”

United should have seen the problem. Instead, it kept turning you down. But after the airline reviewed your case, it decided to change its answer.

“We’ve processed a refund for the extra ticket that was purchased,” the representative told me.

Lesson learned: If you buy an extra seat, always scan the boarding pass. All airlines will cancel the rest of your reservation if you miss one leg of your flight. In fact, this could have turned out much worse. United could have canceled all of your tickets, stranding you.

Christopher Elliott is the founder of the nonprofit Elliott Advocacy, which helps consumers. Contact him at chris@elliott.org or elliottadvocacy.org/help.