Prepaid phone cards make great giveaways, but they're also good for getting something back: customer information. In the past someone dialing the toll-free number imprinted on a phone card heard only a greeting. Now companies that distribute the cards can ask users to answer a handful of questions in exchange for free minutes.

A year ago Peter Barnet wanted to find out how his potential customers--marketing executives at large companies--planned to use the Internet. Normally, Barnet, CEO of Promosis, a $1.5 million promotional marketing company in Marblehead, Mass., would have mailed out surveys bundled with phone cards to encourage his targets to reply. Recipients, of course, could choose to pocket the cards and stiff Barnet on the information, and many of them did.

But last November, Barnet contracted with MHA Communications, a Highland Park, Ill., telecommunications company that specializes in phone cards. Using MHA's interactive voice-response software and telephone switch, Barnet offered his survey over the phone; cardholders dialing in answered questions about their E-mail use and Internet plans by punching buttons or simply speaking into their receivers. Those who didn't want to respond could bypass the survey and still use the card, but those who replied received an additional 10 minutes of phone time. "Of the total mailing of 1,500, about 27% responded to the surveys," says Barnet. "Normally, if we just sent out the survey, we would have had a 3% or 4% response rate."