Xfinity pro extender

Why does xfinity advertise the xfinity pro extender comes with up to two additional extenders when they make it impossible to actually acquire the additional extenders?Even with the pro extender I still have dead spot in my house. I run the connection test and clearly have multiple things that say weak connection. I have taken screen shots and have gone into a store and showed them and they have denied my request and say it can only be prompted by the app. However, the app only prompts the additional extenders at full price when they should be free with the 15 dollars a month that I pay for the xfinity pro extender service.