Not happy!!! Had car 2 days before I heard a knock...

Not happy!!! Had car 2 days before I heard a knocking sound- loud and not constant but enough to ruin the experience of the new to me car- Had to wait 3 weeks to get into service!!! They gave me a 7 year old loaner and proceeded to take my car to the dealer- Friday- all weekend- Monday noon and dealer says they don't hear the noise- I told them I had never driven car more than 10 miles without hearing it!!
I had emailed my salesperson for help in pushing up appt. No response then get a form letter saying the sales process was only the beginning of her commitment to me-