Personal hotspot

Does your cellular provider have a tethering plan?

Have you subscribed to a tethering plan?

http://support.apple.com/kb/TS2756

Some carriers dont support personal hotspots. And may put additional charge to bill. But here is a link to understand a little bit more.

Personal hotspot is not available on the iPhone 3GS. It requires iPhone 4 or later.

It sounds like your phone is jailbroken.

Here are some system requirements you need to have.

http://support.apple.com/kb/HT3574

It is avaialble on the 3GS actually.

http://support.apple.com/kb/HT3574

I stand corrected. It is available on the 3GS as the two previous posts suggest - through USB or Bluetooth.

Thanks.

No problem.