^^^ There are many factor involved and Bell is unlikely to be much help, and the service may not be the problem.
The difference you are seeing could be the due to the settings on the TV, i.e., the calibration is not the same on the two TV's. This was a major factor for TV many years ago but is less of an issue for newer models. Calibration involves tweaking the settings for contrast, brightness, sharpness, colour, tint with a measuring tool. You can do a very simplistic adjustment yourself with a test pattern, but do some research here so learn more about the process and what your options might be.