There's no point contacting the manufacturer, they have nothing to do with the sale of the item and will probably just ignore you or at best tell you it's nothing to do with them.
It could be argued that the network (if, in this case, the phone has been sold by a third-party store and not a network-specific store) has more of a responsibility in this situation as the contract but it's not really their problem either. The agreement between the network and the retailer will state that it's the retailer's responsibility to ensure that all sales on the network's behalf are carried out correctly and legally and, therefore, any issues of mis-selling cannot be deemed to be the network's responsibility.

Consumer laws state that it is the retailer that is the point of contact for the customer, therefore any issues with the manner in which the item was sold are between the retailer and the customer and have nothing to do with any other parties.
(Pope Jamiroquai III, Wed 16 Dec 2009, 22:15, Reply)