iPhone 3G cannot detect wi fi network

Just got my new iPhone 3G a couple of days ago, and was pretty excited until I found out my fone cannot detect our existing wi fi network in the office 😟

Details:
iPhone wi fi address is OK
wi fi is turned on
when on settings > wi fi, the fone doesn't even 'try' to detect any wi fi network in the area.

the 'loading' ring shows up for a second and disappears without detecting any wi fi network, which i know exists in our office building as one of my colleague's iPod Touch can detect and connect to the wi fi network effortlessly...

any ideas guys?

am speculating that my cellular network service provider 'configured' my iPhone NOT to use wi fi connection so i'll be 'forced' to connect to the internet using their 3G service which of course is not free. i don't have real issues using their 3G or Edge of GPRS service to connect to the net, but of course i would just like to be assured that my iPhone is working in its FULL functionality.

any help would be greatly appreciated.

Thanks! 😀