Question: I booked two round-trip tickets through Travelocity from Chicago to Ixtapa, Mexico, almost two years ago. It was paid in full by credit card. Up until the time of travel, the airlines changed our itinerary many times, and Travelocity asked me to call to confirm the changes, which I did on all occasions.

Each time, I was assured everything was in order. I even called two days before the trip to reconfirm our flight.

We arrived at the airport to check in at Mexicana for the first leg of our flight to Mexico City. The remainder of our flight was on Aeromexico. When we checked in, the Mexicana agent told us he could see our reservations, but that we needed paper tickets.

We had to purchase two one-way tickets from Chicago to Mexico City for $948. We had no choice, since we had a connecting flight in Mexico City. All I had were the electronic tickets I had received from Travelocity and Aeromexico, which they would not honor.

I immediately called Travelocity after our return and followed their instructions for getting a refund. When I received no response, I started to e-mail them. It’s been more than a year since our flights, and there’s still no resolution to this matter. I’m at a loss for what to do next.

Colleen Farmer, Crystal Lake, Ill.

Answer: Your ticket should have been completely valid. When it wasn’t, Travelocity should have rebooked you on another flight without forcing you to buy a new one-way ticket, or to pay anything extra at all.

Did you give your online travel agency a chance? Maybe not. If you had phoned Travelocity from the airport instead of paying for the ticket and then waiting for a resolution after you returned from vacation, the company might have been able to save you $948.

Come to think of it, you could have probably fixed this problem before arriving at the airport. How? By checking with Travelocity and your airline 24 hours before your departure.

You called two days before your flight, but most airlines don’t allow you to check in and get a seat assignment until a day before the flight. That’s probably when you would have caught this error.

When you’re dealing with tickets on multiple carriers — also called interline tickets — the odds of something going wrong increase exponentially with each airline added to your itinerary. Being ticketed on Mexicana and Aeromexico would send up a red flag for an experienced air traveler.

Travelocity should have offered you a prompt refund on the one-way tickets you had to buy, of course. It probably was waiting for a refund from Mexicana, and then planned to pass the money along to you. Those refunds can take months — even years.

I contacted Travelocity on your behalf, and your account has been credited in full.

Christopher Elliott is the ombudsman for National Geographic Traveler magazine. You can read more travel tips on his blog, www.elliott.org or e-mail him at celliott@ngs.org.

&Copy; 2010 Christopher Elliott/Tribune Media Services, Inc.