Xfinity employee fraud

I open a mobile line with a trading in my old phone, promise I will receive shipping labels in the mails to returning old phone for credit, been waiting but no label, go back to the branch and find out there is no trading is made with the new phone purchase, and nothing they can do.  Now I have to pay full price on new phone and stuck with my old phone, does anybody know where I can call for this scam???