@Moggy2055: I'm sorry to hear that you have experienced this issue. Please can your send your details in a Private Message to Sam_UK by following the steps in the link below, and myself or one of the other mods will be able to escalate this for you?
@moggy2055 - I been experiencing the same thing even after doing a master reset. Its so annoying as the phone just cuts off through a call or after 5 mins of browsing. I have to wait until it cools down before i can continue. Ive only had at the phone 10 months.