To use Smartphone tethering, it's an extra charge with a limited data allowance. Using a Root wifi tether allows you to tether without this charge, but if they (VZW) sees a horrendous amount of data being used, they will investigate it.Why would your bill be more if you tether a lot?
If they find you guilty of it, they can/will charge you for data usage & could possibly fine you/cancel your account due to breach of contract.