Since XX/XX/XXXX, I started XXXX family plan with a 2-year contract. After this 2 year contract due, XX/XX/XXXX, I went to XXXX store at XXXX XXXX XXXX, XXXX, and changed my plan to prepaid service. But after plan switch, I found XXXX still charged me same money of the canceled plan monthly, in the meanwhile, the prepaid minutes also decreased after each use. I called XXXX customer service for several times to fix it, their representatives agreed to cancel this double charge, but an unreasonable bill which value is {$270.00} resulted from that. And XXXX sold this bill to RPM collection agency to let them collect the money from me.