Hi when you say it switches off does the screen just go black or does the handset shut down completely ? if the phone shuts down completely & its new then take the phone back to where you bought it from as it sounds like theres a fault with the phone if the phone is pay as you go then you are entitled within the 1st 14 days to take the phone back to the shop & get a new phone ! ive got a samsung delphi B3410 & when im not using the phone it goes into idle mode i.e the screen goes black until i press a button then it comes back to life again ... hope this hs been of some use