Bit of a glitch today. Am on the One Plan which includes tethering but for some reason tethering was blocked. Called Three and network technical department called me back to say for some reason the system showed a block on my account for tethering which they have now opened. Just a glitch in their systems but they again called me back to solve the issue as always. But at least it does show their system works for blocking tethering where it's not allowed.