This time last year I bought a phone from Phones4U and took out a new O2 contract. It was not possible to get email working on it. I talked to phone manufacturer's helpdesk and the network operator's helpdesk, neither of which could solve the problem.
I was told I would have to send it away for a firmware upgrade, but I wasn't prepared to send away a brand new phone to a repair centre for 14 days.
I went back to Phones4U and told them I wanted a refund and to cancel the contract (it was within the first ten days, and they were therefore obliged to do so). After trying to set it up themselves, calling the helpdesk themselves, and trying an identical phone, without success, they started processing the refund/cancellation. Before finalising that cancellation they had to click an option on the computer screen to be connected to their head office and I was asked to speak to a manager there to explain the reason for my decision.
He asked me whether I would keep the O2 contract if they gave mea different, higher value handset and demonstrated in the store that email worked. I said yes, it worked, and I ended up with a higher value handset. It turned out that there were known problems with email on that handset/network combination.
The moral of the story is, test all features of a new phone in the first 7 days, and if it doesn't work, take it back and get your money back.
They told me that all phones returned are trashed, which is pretty daft considering that, according to the helpdesk, a firmware upgrade would have solved it, and also, it would presumably have worked on another network.
It was also quite funny that that mobile phone store was in an ex-bank, with extra thick walls, that meant they often had to go to the front door to get a signal!