I thought they blocked it at the network end and it didn't matter what your phone could do.
Three should have tethering enabled on 'the one plan' if they've disabled it I'd phone up and give them a rollocking, threaten to cancel the contract for breach of terms - that usually gets things moving again.
Three should have tethering enabled on 'the one plan' if they've disabled it I'd phone up and give them a rollocking, threaten to cancel the contract for breach of terms - that usually gets things moving again.