Pixelating or blank screen

Comcast has been doing work in my area for a month now and ever since we have had issues with our tv service. It’s constantly pixelating or just shows a blank screen with a message box on it.  I’ve had a technican sent to my house to check everything out and he said it was a Comcast issue at the main hub. Can someone please have this checked out? We had a football watch party Saturday and finally had to stream from Direct TV to be able to watch it on a Roku. I have used the robo assistant and it is no help. Can’t find anyone to talk to report this issue.