Still getting bills after canceling service

I have called twice to cancel service and have a confirmation number for the second cancellation: [Edited: "Personal Information"] but I am still getting bills sent to me. This is the second bill I have recieved since I have tried to cncel my internet service. What do I need to do for xfinity to stop sending me bills? Why do the customer service representatives say they have cancelled the internet service when that is not true? This behavior is very dishonest and seems like it should be illegal.