Hi, I only get that message if I haven't got the Micro SD card in the phone!!!
Have you got a Micro SD card? You cannot take photos without the Micro SD card installed in the phone.
If you activate the Camera Icon, whatever is within the front of the lens will show on the screen - but you can't use the camera without the card.
Just to clarify, your SIM card or provider card doesn't activate the phone.
If you have a Micro SD card - make sure it is inserted correctly.