XPS 17 9700, where can I take it for service?

I paid for out of warranty express service for my Dell XPS 17 9700. The technician ignored the service request and made a quote for something I very clearly did not want, as per the service request and the detailed document sent with the laptop. I called tech support to ask what the problem was, and the person who answered could not tell me anything useful. I asked that the issue be escalated, and the next person could not provide any more information, except rote, scripted replies that he understood my concern, and he was sorry for the inconvenience.

I asked for my laptop to be returned without service, as I need to know what went wrong. Not only was this a waste of time and money, but I don't know where to go for service for my Dell laptop now, as this is clearly unsatisfactory.

I am an IT professional with decades of experience who depends on reliable, high quality equipment and support; I want a technician that can tell me what went wrong and give advice on my resolution options. Where can I take my Dell laptop for this sort of service?