Bad service

I booked a car for two days. i returned it on time and kilos were ok. i got the invoice and there i saw there is a charge for cleaning/valet. Almost R400. I called the call centre and i was told the car needed cleaning. they always was the cars so why now i dont know. I have booked cars for about 10 years now and non of the times i was told my car needed extra wash. i have booked cars while its raining and used untarded roads but have never been told the car needs extra wash. no one is telling me the reasons this time around. why should i get charged this much.