mud and Sand in fuel

Went to Wongar Fuel station 6days ago to fill my tank realised that somethings wrong with my engine. Took my car to Mercedes-Benz just to find out they found Mud and Sand in my tank. This is the second time this has happened at this specific fuel station. I feel I pay to receive a quality standard of fuel. You should really up your game and keep your fuel clean unless you are willing to deal with the damage control. Not even mentioning the post inconvenience caused by not having my car for nearly a week now. Quality and Standard of any customer service is essential.