WiFi is not the same as cell phone cellular service.
WiFi is a short range 50 to 150 feet (maybe more if you are lucky).
It is used to distribute a home or business' Internet connection at a specific location.
All the WiFi owner have had to pay their Internet Service Provider (ISP) for their Internet access.
Typically you local phone or cable TV provider is also your ISP and the charge a monthly fee on top of your existing services. The fee can range from about $20 to $50 depending on the ISP and the service you get.
WiFi transmitting hardware may or may not be included from the ISP, and it may or may not have a monthly rental fee, again depending on you ISP. You can ALWAYS buy your own WiFi hardware, and the run between $30 to $200 depending on make, model, manufacture, features, ease of use, number of WiFi frequencies supported, number of frequencies supported at the same time, maximum transfer speeds, number of concurrent WiFi users handled, etc…
You can also get free WiFi at various coffee shops, bookstores, public libraries, shopping malls, etc…
There is also a device called a MiFi, which is sold by cell phone carriers. The MiFi is a mobile WiFi the uses the carrier's cellular network to give you Internet service. MiFi contracts are generally more expensive per byte transferred than a home ISP connection, but they give you Internet access to an iPod Touch anywhere the cell phone carrier offers cellular service.
Most smart phones also offer, for a monthly fee) a tethering service that effectively turns them into a MiFi, but if you have a smart phone, you generally just use it to access the Internet , although business users like to connect there laptops when on the road this way.