Was told it's fixed but it wasn't

Noticed on Wednesday that my stepway was showing a warning sign when I turn the key on the ignition but it would disappear a couple of minutes after I start the car.got worried and booked it in at your dealer in centurion.took it there this morning.they called later in the day and said the problem is fixed. Went to fetch the car and I left. Got to work and parked the car .when I was going home I decide to check if the sign will show after I turn the key.guess what,the sign was there and once I started the car it disappeared. Drove and came back home . switched off the car and took out the key then put the key back in and turned it and the sign is still there. Started the car and after a few seconds the sign disappeared. Now I would like to know what exactly was fixed if the sign still keeps appearing.its so frustrating to book the car for the whole day,be told that "it's fixed"& only to find out that the same problem is still there. What exactly must I do now?. Renault please advise me.hpw do I drive my car when it has a warning light that your technician said it's fixed when it's not?.