Make sure what you buy

Im was interested in the Audi Q7, i asked if i can take the car for a diagnostic test (on my account and I will pay diesel) so that i know what im buying, the guy on whats app says no, i cant cause i need to take it as it is. I said according to law if you are registered as a dealer i can ask to take it, and if you registered as an auctioneer i take it as is. He keep saying i must take my business elsewhere. I also asked if the owner can call me, then this guy says he is the owner and that i dont want to listen, and that they have other rules. I will not recommend them just because i feel they are not honest and dont want you to know that the cars might have problems.