Back in the day, I had to sell some BTC to pay the fabrication facility makiing Bitfury USB miners.  I used Coinbase.  They fucked up the order which was going to delay my money for 3 more days which would have killed my timeline.  I spent a couple of hours finding their top secret address and ended up knocking on their top secret door.  Brian Armstrong opened the door personally after I spent some time talking very loudly with him through it.  After threatening him a bit, he finally saw it my way and gave me a check to go away.  My favorite part of the exchange:

Brian (to nameless programmer on other side of the door):  "This is why we don't want customers here".
Me: "I can hear you"
Brian: "Shit"   - pause - "OK, come on in".