Freezer worked fine but the Refrig. wasn't getting cold

My husband first replaced the Defrost heater and the fridge still didn't stay cold. We had to defrost the freezer once a week and the fridge would stay cold for a few days, but after we replaced the Thermostat Assembly it worked GREAT! Thank you all for your comments and suggestions it saved us hundreds of dollars having to replace an, otherwise, perfectly fine fridge. Good luck to you if you have this problem, it was sooo fast and easy to replace these parts and totally worth the money.