samsung side by side fridge freezer not cooling down?

I have a samsung model sr-s2025cvw fridge freezer which does not work properly my freezer temp goes up to 10 degrees or more so does my fridge if i turn the switch of at the plug for a few minutes then turn it back on it will work for a day then it will start to rise in tempruture again.
I have seen on sites elswhere i may need to replace the yellow sensor cable and fridge defrost isolation sensor/defrost termination wire black/red one. vIs this the problem im not sure can anyone help me.. also where can i buy these parts as ive searched online and cannot seem to get hold of them... please can anyone offer advice..