Billed for non-return phone in error.

I was billed for a non-return next trade in device.  I chatted with 2 chat reps ( i have the transcripts), who assured me the phone had been received and had not been processed through the system yet.  Since, I have chatted with 2 more reps, who tell me it was not received.  The last rep gave me a case number and told me someone would contact me within 7-10 business days.  After those days past, I chatted again and was told the case had not been worked yet. We are now several months past the issue and i still do not have a resolution or the credit the rep promised me for the return device.  I do not know where to go from here. Can the BBB help me?