Double Device charges

So for 22 months Verizon has been charging me for two device payments on a bogo phone deal I started with them.  I called the reps first time I saw it on bill they said they would refund it and it wont be on there anymore. Never really thought about it after that until recently I checked my bill again because I know I'm coming close to my 24 months payoff so I can upgrade and it was still on my bill every month since I started the account and never did I receive that refund either!! Now everytime I call customer service they said they will have the supervisor call me back in an hour it's been 5 days every day same answer, "we have to call you back". So now that they owe me over $800 no one wants to talk? Do I need to file court papers to account resolved? I need answers...

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