Yes the phone is yours, it has nothing to do with your contract with vodafone, its just a extra for taking out the contract and neithe it nor its value are mentioned anywhee in your contract

@snaps, you have to wait until they charge you before you can cancel, the notification text alone is not enough to be able to cancel your contract.

And if anyone does decide to cancel it needs to be in writing along with a check for any outstanding charges marked "full and final settlement" and then cancel your DD.
They will never let you out by calling them on the phone, and will try and tell you that you can not cancel your contract without paying a fee.
So if you do decide to try canceling you will need to be prepared to go to court and argue your case (although chances are they wont want to take it that far for fear of setting a president that will let others out of their contracts)