HI Anonymous, Call up the service provider and they will help you how to deactivate the GPRS as you have not mentioned the phone you are using.
Hi Georgie, You too have to check whether the service is activated or not. First activate the Internet connection.
From the main Home screen, press MENU, and then tap Settings > Wireless controls. Make sure that Mobile network is turned on. Tap Mobile network settings, and then check the following: Automatic setup is turned on. The name of your mobile operator is displayed in the Network operators item. The right mobile network is displayed in the Access point names item. If it's not the right network, see your phone's user guide to find out how to add a new access point.
Turning the data connection off
You can turn off the data connection to help optimize your phone's battery life or to save money on data charges.
From the main Home screen, press MENU, and then tap Settings > Wireless controls. Turn the data connection off by tapping the Off/On switch of Mobile network. (Tap this switch back on if you want to connect to the Internet again.)