@Amara7: To begin with please press the Volume Down and Power buttons together for around 10 seconds until the phone restarts to refresh the device and address any temporary issues. If the problem persists then please open the Phone app, dial *#0*# (star, hash, zero, star, hash) into the telephone keypad and select Subkey. If you press the Home button, does the screen respond to the button press by changing colour? If not then please visit an authorised Samsung Support Centre to arrange for the phone to be inspected. To find your nearest one please follow the link below, select 'Mobile Device' and enter your post code.
http://www.samsung.com/uk/support/servicelocation/
http://www.samsung.com/uk/support/servicelocation/
