pixilated TV screen

We have intermittent "ghost" images from previous screens that carry over into the current screen. We also have intermittent pixilated breakup of motion on our screen. I've spent numerous half hours with text chat that always end with something along the lines of "Your problem is fixed.  Thank you for contacting Xfinity support." But the problem isn't fixed. I finally got to a person yesterday and an appointment was scheduled Monday between 3 and 5 to fix the problem or replace the TV box we rent from Xfinity. Then my wife got an email saying "Your problem is fixed. Your appointment has been cancelled." But the problem isn't fixed! We had the same issues, still intermittent, after we received the email. Getting a person to talk to seems impossible. What should we do next?