Q: Tethering with USB?

I have just upgraded from an iPhone 3G to an iPhone 5.  Internet tethering (now called Personal Hotspot) to use up data credit on my phone account worked very well on my old phone.  However when I plug the iPhone 5 cable into my MacBook Pro it is simply not recognised in Network Preferences, as my old phone was.  With the 5 I can tether with either Bluetooth and Wi-Fi, but the response is dreadfully slow and subject to hanging.  I have spent hours on the phone with Telstra (Australia) and Apple with no success.  Has anyone else encountered this problem?  Can anyone help?