Please help me/

I have two teenage kids; 18 and 15. They just don't seem to understand about RSD. I have talked with them about this; however, it just doesn't sink in. When I was their age, my grandmother had cancer; so I can understand that they don't grasp it.; However, they continue to be cold and unresponsive to my needs and concerns. How can I possibly convey to them the magnitude of this crippling disease and also relay to them the coping skills they surely need? I have resorted to turning their cell-phones off as a matter of discipline; in which I feel horrible about. They continue to "diss" me even after I have tried to enforce my (not horrible) threats to them. I tend to over-compensate to make up for my shortcomings. In which I feel has led to this situation. I would appreciate any advice and/or lecture on this subject. I am heartbroken over this. So, any advice is more than welcome~ Thanks!