I recently was scheduled to fly from Cleveland to Las Vegas on Spirit Airlines. Before I boarded, a gate agent announced that the airline was looking for volunteers to give up their seats because the plane was oversold.

Nobody was volunteering since it was a holiday weekend, and after several announcements, my companion and I decided to step forward. A Spirit representative promised that the airline would get us home Tuesday night instead of Monday night - we originally were going Friday to Monday - and we would be given four vouchers to use anytime and anywhere Spirit flies.

We asked several times about restrictions and booking, and the agent adamantly said that we could go anytime, but that we had to call to book the new flights within 60 days.

The airline actually sent six vouchers. We called with several dates for February, March, April, May, and June and were told that no voucher seats were available on any flights to San Francisco or to Orlando or Fort Myers, Fla. - the three places we chose because we have family there.

We gave Spirit the dates for every weekend in all of those months and were told there were no seats, even though one agent told us the flights were empty at this point. Now we have six vouchers, and no way to use them. We were able to book two of the vouchers, but I feel like we were scammed, because we can't use the other ones. Needless to say, this is very upsetting. Can you help? - Kathy Davis,Willoughby Hills, Ohio
A: Spirit's vouchers have significant restrictions, something the gate agent should have told you. And by the way, Spirit's vouchers are more restrictive than most. You have only 60 days to make a reservation. The industry standard is a year.

I don't know what the airline employee told you, but let's break this problem down. Spirit overbooked its flight. This should not be allowed. An airline should sell only as many seats as it has. But the federal government, which regulates airlines, allows this practice. So they do it.

If no one had volunteered to give up his or her seat, then Spirit would have had to offer a refund under federal regulations and fly that person on the next available flight. That costs the airline real money, so in order to avoid it, a gate agent will try to entice someone to volunteer. And what matters isn't what the agent says, but what the vouchers say. All of the restrictions for your new vouchers would have been spelled out.

This is not a Spirit problem; it's an airline problem. As long as airlines can sell more seats than they have available, this will continue.

You could have sent a brief, polite email to one of Spirit's executive contacts (http://elliott.org/company-contacts/spirit-airlines/). The airline is trying to improve its image, and you may have persuaded a considerate manager to give you a little extra time with your vouchers.

I'm troubled by the disparity between the agent's words, promising that you could fly "anytime" and the reality, which is that most of the voucher seats were unavailable. That doesn't seem right.

I contacted Spirit on your behalf. A representative thanked you for volunteering to give up your seats. "The vouchers given at the airport do have some restrictions," he said. "However, they are not typically such limited options. I completely understand their frustration."

Spirit voided the original vouchers and issued new round-trip vouchers with fewer restrictions, so you can still take advantage of the trips you were trying to schedule.