If it works on cold wash only program, then I am afraid, the heating element is faulty and will need replacement.
However, if the issue is still there on all programs including cold wash only then this, indicates either the drum belt has snapped, the motor and/or motor control is faulty and will need replacement.
Please try this to solve the issue:
You will have to unplug the appliance and pull it out, then remove the top off the appliance.
After it is removed, check if drum belt is intact, if that is fine then plug it back.
Now, keep your hands off electrics and select any program, if drum will not tumble give it a bit of push with your hand.
If it starts working then motor control is faulty however, if it will not start rotating then motor is faulty and will need replacement.
Samsung provides 5 years warranty, on its appliances hence, if it is under 5 years old you may call Samsung to book in warranty repair.
Alternatively, you may call Samsung at 0333(###) ###-####to book repair.
If there is anything else I can help you with, please let me know.