I've had some minor experience with a fridge not cooling down as well as it should in a rental house, while at the same time the freezer was doing just fine. Since I have a neighbor who works at an appliance repair shop, I asked him to go fix it. He said no, it wasn't worth his time and told me how to correct it. Maybe this will help you.
There is a flapper between the refrigerator part and freezer part. All of the refrigeration takes place in the freezer section. The cold control in the freezer determines how much total refrigeration goes on. The cold control in the refrigerator controls the amount of opening of the flapper. Convection moves the air from freezer to refrigerator. So, if you need the refrigerator part colder, you might consider turning the refrigerator control to about the mid-range (at most) position and turn the freezer control up higher.
You may already know all this, but I sure did not.
I bought a small thermometer from the auto parts store and took it with me when I did the cold control adjusting. In just a few minutes the refrigerator was heading for the right temperature.