Stay away from Xfinity mobile

we bought a new iPhone from their store with trade in of old iPhone. They were supposed to apply 600 off on the new phone, which they did not. Whenever We call customer care they accept its mistake from their side and raise a ticket for same. But ticket gets closed without any action. This is done 4 times already now. Moreover they have stolen our old phone as well as they kept the phone without applying credit. Stay away from them