Make sure that your internet/APN settings are correctly configured:
http://community.48months.ie/t5/Need-Help/Internet/m-p/34493#M12560
Did it ever work?
If so then you seem to be using a Samsung Galaxy phone and these have an unfortunate habit of spontaneously losing settings necessitating their reconfiguration.
Nobody has ever explained why/when this happens - perhaps when the phone automatically installs an update or something?
Hope this helps.
