Bad customer service, Mercedes Benz Sandwon, Brayston.

I bought a pre-owned car with the dealer, the car has a crack at the front and it was not visible due to the black stripe that is in the car. I noticed that when washing the car 7 days after collection and called the lady that assisted us to buy the car. she committed to get the windows fixed, I am of the opinion that this was to pass the 14days period which a customer has a leeway to return the car if something is not okay about it. I never got a response from the dealer for 7 days until I followed up when the replacement date will be. that is when the sales lady told me that they did not approve the request. because of an investigation that failed to prove that the car had a cracked window. I doubt there is any investigation done as there was nothing to prove that the car had a crack since collection. but the crack was at the bottom of the window where there is the black stripe. not easy to notice. this reflect that one must not buy pre-owned cars from dealerships like them because they are more interested on benefitting then. they don't care about their customers burden after.