No Customer Service

I have been trying to contact uber since Saturday, you cannot get to speak to a customer service agent, I never booked the ride, a customer of mine did, (he then defaulted on payment) to pick up my product, the customer never paid the driver, now the driver is holding my product hostage, we agreed on an amount for the driver to return the product, I paid him, and now he wants more, he is shouting and swearing at me, but I cannot contact Uber head office or other person, they don't even answer their facebook messages.