Setting wifi as primary internet medium

Hi,
I am a newbie to BB. i have a few issues..

1) How can i make my BB to use only wifi and not Wap or 2g (over Vodafone)... I connect to Wifi and then surf the appworld or the web but still i end up using a services from my service provider that i dont intent to

2) When i try to browse to web using Hotspot Browser or Vodafone Live i get the error message unable to connect .

Can some1 kindly advise the settings that i have been missing

BTW . I am using BB Curve 8520 - V 5.0.0.1036