The fidge/freezer is switching on

Question

The fidge/freezer is switching on but is not getting cold. It is a new fridge that was replaced but never collected from me so now I would like to get it repaired. I am told that the fridge needs gas or a gas container, what I would like to know is how much would it cost to refill/replace container and also could it be anything esle that is stopping this from operating?