Beko frostfree fridge freezer not working

My mum has a Beko frost free fridge freezer, which has suddenly stopped working. It is approx 4 years old. The light inside still works and it sounds like it is on but neither the fridge or freezer get cold.
We have no idea what it culd be. A guy at a local shop said it is no good (without inspection) and recommend she bought a new one, he just happened to be selling them! She cant really afford a new one........any help will be great. Thanks

with out knowing model number i would see if had thermostat and replace that

when u say it sounds like its still on are you refering to a fan inside or the compressor ?? if the compressor is running but its not getting cold it could have lost its gas