Yes you can definitely switch to Vodafone network from 3 network. But what is the specific model of your mobile phone? You must unlock your mobile phone using unlock code before switching the network. you can get the unlock code either from 3 network or from any trusted vendor online. For example, You can get the accurate unlock code for your mobile phone from www.classicunlocking.com at low cost with easy instructions on unlocking process. All the best mate.