Dial-a-phone.co.uk has introduced Automatic Cashback plans on 3 and O2 network mobiles. This is ideal if you want to buy a contract phone but dont want to bother / worry claiming cashback.
Also, for every transaction, you can get £50 cashback through Quidco.
100% Risk Free cashback which is also guaranteed but the cashback amount would be less than what you would get from other sites. Choice is yours !