TNT network HD channel pixelated

My HD TNT channel is hard to watch due to pixelation. Sometimes you can not even tell what channel you are on or what is happening. It only seems to be the TNT network as far as I can tell. I have contacted Xfinity, I have checked my connections, I have reset my box now about a dozen times, and all I am being told is they can't seem to find a problem. Surely for what I pay a month to keep my cable there must be some solution for this issue.