Are you looking at fixng this yourself?
As if the fridge isnt cooling but the freezer is then its usually the freezer evaporator blocked up with too much ice stopping the air flow into the fridge section.
What you need to do is either empty the freezer and from there remove the back cover in there.
Behind the cover you will see the evaporator. If this is blocked up with too much ice then you need to use a hairdryer and defrost it from there till its all melted.
Or if you dont want to go removing panels then you need to empty the freezer still and turn the appliance off for 24 hours and leave the freezer door open.
This will allow the ice in there to melt itself so place a few towels in there as you may get a bit of water from there.
Once its all clear retry it and see how it goes from there. Fingers crossed its a one off overfreeze that caused this fault.
But if after 2-3 weeks later it does the same then theres a fault on the auto defrost side which could be either the defrost heater itself or thermal cut out.
But try the defrost as above first and see how it goes from there and let me know.