( *** REQUIRES ROOT ACCESS *** )
Usually mobile providers know if you are using WiFi Tethering or not and they may apply additional costs! If you want to avoid let them know you are using it just check your value, if it's '0' everything is ok , otherwise just press 'Write' to set the value! Now you can use Tethering without additional costs! It is supposed to work on almost all providers / countries so just give it a try! No guarantee! Use it at your own risk, but the only thing that can go wrong is that you need to pay the teehtering as usual but I'm sure you will not :-)
If the DUN value is set to "null" it means that the tethering iformation will be sent to your provider
If the value is set to "0" (this app do that) the information will not be sent to your provider.
So everytime you need to share your mobile connection check with this app if the value is set to "0" (press the READ button) if not use the WRITE button to set it correctly, then share your mobile connection with every devices you want! This application does not create a WiFi Hot-Spot so once you set the value start your Tethering from the Android built-in function.This App is just for testing purpose so I'm not responsable for the use you made.
Please also consider that this is a first release and it's FREE so it might not work in some cases, just let me know and I'll try to fix it!