Originally, some Nokia mobiles had an i after the number, and I recently saw most other makes adding some. In a car the meaning is obvious, but on a mobile phone? None looked any different, and I could have asked in the shop, but I trust the reliability of people here more than some staff in phone shops.
Good theory Gilf, but I don't think many don't have internet any more. I'll try my local emporium if necessary, but unless you get the boss, most staff will just try and sell you an upgrade :D