It does seem that the PN network is configured to require certain setting on some phones.
My previous phone worked fine but the new one doesn't without changing the settings.
There are 2 possibilities (3 if you include rooting the phone - but we won't go there!) :-
1) add DUN (dial up networking ) to the APN you are using for PlusNet data access. This is done by adding ",DUN" to the APN type ( without the quotes ). Didn't work for me...
2) change the global setting such that DUN is not required for tethering, this worked for me!.
You need USB debugging enabled and ADB installed on a PC
To do so, you'll need the Android Debug Bridge. You can install the Android SDK. Go ahead and download it from Android Developer site.
Once installed, make sure you have the correct USB driver for your Android device. To verify, hook up your phone to your computer. Open command prompt (I use Windows, if you use Mac, open Terminal). Type in the command:
You should see your device listed. This is the proof that you have the correct USB driver.
Here's what you need to do:
1) Go to Android Debug Bridge Shell with the command adb shell
2) Inside adb shell, type in the command settings put global tether_dun_required 0
You are done!! You can type exit to exit from adb shell.It's quite common
NB the first time you run 'ADB devices' the phone will ask you to authorise the PC to access it.
PS You'll probably find much better explanation and instructions by googling 'tether_dun_required'