2004 Renault Scenic

Had heater fan repaired under warrantee some time ago. But realised 2 days later air con didnt work any more. They say they removed most of the dash to get to the heater fan, removed debrie causing noise. Since then there is no response from the air con switch doesnt even get the little red light on when pressed.I was wondering if they have left a plug undone or broken something while under the dash like the rheostat, I have been told that this item is by or attached to the fan unit itself they are trying to say that it couldnt have been working before this, but I know it was in perfect order its like its none existant I have checked every fuse in the car including main fuses under the fuse box in the engine bay, glove box and, underthe passenger seat, any ideas would help