Telephone number: +18004270106
(8004270106, 018004270106)

The message said they want me to contact them for an appointment to check the cable box.

I called the actual Comcast customer service phone number and they said the call was legitimate and was made by the Comcast dispatcher team.A ticket had been opened on my account stating that 'ingress issue found at locations. Some services at this location may operate at a reduce capability doe to a high pass filter installed at the tap to reduce the ingress problem An appointment will need to be scheduled for a tech to go to the location and correct the ingress.