Are you just having to leave a voicemail? Is there some sort of chat / help function you can use? Take a screen shot of their responses.
Send an email spelling out the issue to as many vroom emails as you can find. Explain the situation, the lack of responsiveness and that you will be contacting the Attorney General's office in their state and yours if this is not resolved in 14 days.
jenny.watson@vroom.com (Chief Experience Officer)
patricia.moran@vroom.com (Chief Legal Officer)
legal@vroom.com (why not try)
john.caine@vroom.com (Chief Conversion Officer) website says his job is to seek out and alleviate the pain points in the car buying process.
peter.scherr@vroom.com (Chief Marketing Officer)
I can't remember what state you are in but reach out to the consumer protection agency (Attorney General) in your state as well as the state that Vroom is HQ'd in (NY from what I can tell).
Light them up on twitter, etc.?
Good luck and keep us posted.