Billing Issue

I need help with a warranty exchange issue. I sent back the device in the time allowed with a tracking number and was charged 769.00 for the warranty exchange device.i have the text message saying the device was scann Apparently they received an empty box. I have called over 35 times and spent over 40 hours on the phone, chatted and went into the store and still no resolution. I get hung up on, transferred numerous times to the wrong department and told it’s not there issue. I can’t even get the address or shipping label to return my phone I received for the exchange . I just want this to be over and resolved . Worst experience in my life for customer service. Please help!