Here in the US you can dial 1800SAMSUNG or ask at the phone's support counter.

https://www.google.com/search?q=EK-GC100+in+demo+mode&oq=EK-GC100+in+demo+mode seems to write there are some permanently in Demo mode. How to tell?

"Look at the bottom of the camera . If the SKU ends in DU. that means it is a dummy and stolen."
These are not fixable since they are hard-wired and coded to stay in demo mode to keep them from being valuable or sold.