Can you be a little clearer?
You're already home with the phone and a signed contract?
If that's the case, then there's very little they can do and if you took the phone back, then more fool you.

If however you have seen a price and they then refuse to sell the product at the price, that's probably perfectly legal as most retailers have a disclaimer in/on their catalogues/leaflets that states that prices displayed, whilst accurate at the time of printing, are subject to change at any time with no prior notice and, therefore, the prices on their till/computer systems are final (with exceptions for the likes of manager's discretion etc).
Also, a retailer is (I believe) allowed to remove an item from sale rather than sell it at a specific price.

As for the contract, it may not mention the model of phone.
The reason being that the contract is an agreement for the network to provide a certain level of service for a specific cost - the handset is not an integral part of the agreement, hence why the loss of, breaking of, damage to or any other problems with the handset is not grounds to cancel the contract.
(Pope Jamiroquai III, Wed 16 Dec 2009, 22:09, Reply)