quick question 
my dad has an iphone 3gs on billpay, he got a message saying he could upgrade to an iphone 4s for like 100 euro.. he said i can have the iphone 4s when he upgrades and he'll keep his phone because he's happy with it. my question is, i have a sim card (pay as you go) with vodafone and will that work in the phone that was meant for a vodafone billpay? or will i need to get it unlocked etc etc.. thanks for replies 
my dad has an iphone 3gs on billpay, he got a message saying he could upgrade to an iphone 4s for like 100 euro.. he said i can have the iphone 4s when he upgrades and he'll keep his phone because he's happy with it. my question is, i have a sim card (pay as you go) with vodafone and will that work in the phone that was meant for a vodafone billpay? or will i need to get it unlocked etc etc.. thanks for replies