Saterday service car drop off time always wrong

Second time this is happening. Reason why I phone Renualt to confirm what time I should bring in my car for a service on a week end. Being told to bring in car from 7am to 8am arrive at gate 7:20 am just to be told sorry we open at 8 no one is even here to claim car. Do not twll people to bring in their car between 7am and 8 am if you are not here to claim car