Is it their Box, signal or maybe my TV.
The way to see if it's your tv, connect another source to the same input. To tell if its the cable signal, you will have to have them come out and check the signal.
Honestly, it's likely you just got another bad box. My cable company uses Motorola boxes instead of the SA ones, but the last time I had a problem with one, I returned it, got another, and the second had the same problem. Took it back, got a third, and that worked fine. So it's not unusual to have two bad boxes.