I too have a o2 contract and i have the samsung s300 model. If u are connecting by Gprs, you havent set it up properly in the settings and u will be charged for the bytes that u download to your phone.I use Gprs on my phone but i use my o2 pay and go sim card, at the moment they is no way they can charge pay&go customers for this service which is a fault at o2 end, 500 wap minutes a month soon go ,so if u havent got a o2 sim and u use the phone alot for the internet, i surgest u get one cos its alot quicker for loading pages and downloads and its free..To set it up you have to send the Gprs settings for pay&go to your phone from the o2 site and save the settings and use your pay&go sim card and it wont cost u a thing....make sure u keep above 30-40p on your phone so u can keep using it....Hope this helps !!!!