Who I have the same questioned this topic

I traded in two phones in December. I have both UPS receipts that say "delivered to dock". I verbally have been told by two separate Verizon representatives that the phones were received. I was getting an email saying one phone was not received. That stopped after a telecon with a representative who assured me both phones were received by Verizon. I received an email today saying I would be charged $650 for one telephone because it was never traded in. I HAVE TO UPS RECEIPT STATING IT WAS DELIVERED TO VERIZON. I have spend countless hours on the telephone trying to get this resolved. I am at my wit's end. How do I escalate? I go through the phone systems, wait the requisite multiple hours to get a representative on the telephone, who tells me, after referencing my ticket number, that all is resolved. Meanwhile I am getting billed for the phone that was returned, but not acknowledged. I even have Verizon auto generated email that indicates receipt. HELP! any suggestions? I am thinking of picketing local office, kidding, not kidding.