Over the past month or so, newspapers and TV screens have been full of reports about free Internet calls. But as with most “free” things, these offers should be called “free with some strings attached” or “unmetered Internet calls”.

Traditionally, Internet calls have been made on a metered or per-second basis (pay-as-you-go), most at local rates. US residential telephone users have had an unmetered local call service for years - a monthly fee for unlimited local calls, or a “pay-and-go” service. So it’s not surprising US Net users spend more time on the Net than their UK counterparts. So will the 20 companies offering “free” or unmetered calls for all or part of the day or week change the way we surf?

Although the Internet search engine company AltaVista made headlines when it announced its free service in March, it was not the first company in Britain to offer unmetered Internet calls. That honour goes to screaming.net, launched by retailer Tempo last summer. Subscribers to screaming.net receive free Internet calls at weekends and evenings provided calls are made through telecoms operator LocalTel.

AltaVista’s service, expected to start next month, will charge an upfront fee of pound;35 to pound;50, and an annual renewal fee of pound;10 to pound;20 for unmetered Internet access. However, Andy Mitchell, AltaVista’s chief executive, says there will be some restrictions, for example your Internet connection could be terminated if there’s no online activity after several minutes (designed to prevent users staying online 24 hours a day, seven days a week) and he hints that users may initially be limited to a set number of hours per month.

The next company to announce free Internet calls was the cable and telecoms company ntl, with ntlworld. There are two ways of receiving its free Internet service. If you live in an area where ntl operates, you can sign up for a cable TV and telephony service from pound;9.25 per month. Those living outside ntl’s franchise areas will need to buy a pound;10 telephone adaptor, which routes BT calls to ntl’s telephone network, and spend at least pound;10 a month on non-Internet calls.

In February, BT Internet offered its subscribers unlimited Internet access at evenings and weekends for pound;9.99 a month. And in March, BT introduced SurfTime for Internet Service Providers, covering residential and business customers. There are several variants of SurfTime. A package aimed at occasional Net users costs pound;9.25 a month line rental, with Internet calls costing between 0.6p to 1p a minute depending on the time of day and day of the week. A monthly payment of pound;15.25 gives unetered calls every evening and weekend. For unmetered Internet calls all day, seven days a week, BT SurfTime offers several packages: residential users pay pound;29.25 per month, business users pay pound;29.74 a month. For ISDN users, the monthly charges are pound;46.99 and pound;46.34 respectively. (However, these are wholesale prices, so the charges you pay may differ).

Freeserve, the free Internet service provider of Dixons, is also planning to offer unmetered Internet calls from May. It will have two offers: BT users can pay pound;6.99 a month for unmetered calls during off-peak hours and weekends; or customers can route their calls through the Energis phone network (by using a free adaptor box that plugs into a telephone or dialling a code) and spend at least pound;10 a month on voice calls for unlimited access all day, every day.

So is it worth opting for a free service? BT’s Schools Internet Caller (SIC) costs pound;790 a year for an ISDN connection and unlimited calls from 8am to 6pm (excluding weekends and holidays). But the SurfTime ISDN business rate is pound;556 a year for unlimited calls any time, any day. It sounds tempting, but Tim Clark, RM’s Internet marketing manager, says schools should be wary about opting for free packages: “These packages are really aimed at residential users rather than businesses, which is what schools are. These free services are likely to be used heavily so it could be difficult for schools to get online because of the sheer number of users. And the free services are designed to carry as much traffic as possible, so they are likely to be slower than a conventional service.”

Clark adds that the free services, with the exception of BT, offer dial-up connections that cannot support a school network, and secondary schools should be looking to use broadband (high-speed) connections. “A few deals require users to make a minimum amount of voice calls on the same line, but schools often have separate voice and Net lines. And many of the suppliers don’t offer much education content or filtering,” he says.

He adds that RM offers primary schools 15 hours a week of Internet ISDN calls for pound;395 a year, a deal the new services find hard to match; even an ntl spokesman said RM’s offer to schools of unlimited access on a 128K line for pound;1,500 a year is a good bet.

Clark is not wholly critical of the raft of unmetered or free Internet call offers. He explains: “They can be compelling for residential users, but you have to check the hidden charges are worth it. But the main thing is these initiatives will lower the floor for telecoms charges, which will benefit schools.

“My advice is for schools to wait,” he says. “No business would rely on a free service, but schools will find their Internet call charges will fall as a result of them.”