Q: I booked four tickets from GoToGate for AirAsia flights from Singapore to Kuala Lumpur, Malaysia. The site displayed a price of $400. After I filled in my details, there was a lag in the website, and a new price of $1,002 popped up through another window in my mobile browser.

I did not want to make this booking anymore, but it wasn't immediately clear how to cancel. GoToGate charged my credit card $1,002.

I checked the AirAsia site, and the same ticket costs $500. That means GoToGate is marking up the tickets by 100%!

I called GoToGate the same day, and a representative told me they could not refund my ticket. They recommended that I contact AirAsia. But an AirAsia representative said I have to go through GoToGate for a refund. Can you help me?

A: Airline ticket prices change constantly, but they should not change after you push the "book" button. This was definitely unusual.

It's also important to be extra vigilant when you're booking tickets. Make sure you don't buy your tickets unless you're certain of the price, which, as I already mentioned, can change in the moments before you book.

Here's what should have happened. Between the time you clicked on the fares and the time you booked your tickets, GoToGate should have explicitly asked if you wanted to continue with your purchase. Only then should it have charged you $1,002.

Instead, you had selected your fare and finished your purchase by filling in the passenger names when the online travel agency decided to change the price.

GoToGate was not marking your tickets up. It's far more likely that the airline had run out of fares at the fare you saw, and GoToGate was just updating the price. But there was more to your story.

Online travel agencies like GoToGate have their uses. You can run easy price comparisons through a website like GoToGate to quickly find the lowest fare. Sometimes, online agencies can also offer attractive package deals that help you save more money. But I also get a lot of customer service complaints about them. They often behave like balky vending machines, at least when it comes to service.

I list the names, numbers and emails for GoToGate's customer service managers on elliott.org. A brief, polite email might have fixed this for you.

I contacted GoToGate on your behalf. A representative responded, "Due to a manual mistake, we offered the wrong price to the customer. We have now mailed and apologized, and will also refund the customer's ticket in full."

Christopher Elliott is the founder of Elliott Advocacy, a nonprofit consumer organization. Contact him at elliott.org/help or chris@elliott.org.