Iphone 4s 32GB locked to Vodafone 2mths old -

I am selling my almost new, unscratched (had seal on and cover since day one) Iphone 4s 32GB phone due to the fact that I have moved house and get no signal on Vodafone at all!!! Therefore I have bought myself out of my Vodafone contract and now have an Iphone on O2! It works perfectly and in brand new condition.