Wi-fi is not a service as such, your phone either has the ability to pick up wi-fi or not. No bolt on will change this.
See it as a wireless modem in your phone and if it can pick up a signal... its free!
Mate, your not only on the failboat, your the bloody captain!
Cloud, btopenzone etc, both wifi network services, both not free UNLESS YOU HAVE THE WIFI BOLT ON IF YOUR NOT ON AN IPHONE CONTRACT.
We're gonna need a bigger boat.
to the op, simplified version of this thread:
Salesman in shop has no idea what wifi is or how it works.
You have no idea what wifi is or how it works.
JJ appears to think he does but actually doesn't/has got confused.
The remainder of people know what they are talking about but the thread has gone round the houses to give you the information you require, so i'll stick it all in 1 post:
If you get a phone, on the simplicity tariff with the web bolt on, you will get unlimited (subject to fair usage policy) time to spend on the internet on your phone under edge/GPRS/3G internet connection.
If you get a simplicity tariff with the web bolt on, the wifi connection in your house, your friends house, your dads nans house, all free, even your next door neighbours will be free if they've not got a password on it.
Wifi networks in public places which come under the "cloud" or "btopenzone" ownership (it will tell you this when you try to connect normally) will charge you if you connect to them because you don't have the bolt on that gives you free access.
So in summary, unless your going to be sat in mcdonalds filling yourself with fat whilst browsing pornhub then you should be fine, i have never used a wireless network outside someones house as i don't need to, 3G etc is fast enough for what i need when i'm out of the house, for most peoples lifestyles it should be perfectly fine.