Hi, I have Range Rover Sport Supercharge 2008, Battery problem

What is your question?

Hi, I have Range Rover Sport Supercharge 2008, I am facing a problem with the battery, I change the battery every month and some times every week. If I keep the car for three days in the garage the battery is gone. if some one know or face the same problem so can help me or advise what to do? I took it the dealer and he confirm me that every thing is fine based on the computer test or the diagnoses systems that they used.