How to get ATT to contact Newgistics regarding LOST PHONE

I sent back an unused Galaxy Samsung, paid outright $760, to ATT.  Newgistics site shows it bouncing around the country for a year!  ATT only just confirmed they never got the phone after months of calling.   So Pitney Bowes owns Newgistics.  They told me that I need get ATT to contact them about my phone, as ATT is their customer.  Does anyone know of a number or email or address for ATT so I can get someone to contact Pitney Bowes about the whereabouts of my phone?  I would like my money back, though I highly doubt anyone on the planet cares.   Thank you.