As far as I know, you cannot cancel it unless you have been on that particular contract for 12 months - regardless of your time with the company - and you will have to pay for the remaining rental. Would it worth swapping your phone to a pay as you go and selling it on ebay to cover the costs of the outstanding rental? Then getting a new phone with your new contract? I have got round it that way. Alternatively, like you have said, reduce your contract to the lowest tarif if your contract allows it. Best bet is to look on their website , or give customer services a ring.