Panasonic TX32DT4C - problem with channel number display

I wonder if any one can offer advice or help with this.  I recently bought a
Panasonic TX32DT4C television and I am very happy with it apart from the
niggly problem that the channel number displayed on the top left hand corner
does not disappear.  It disappears perfectly well when I am on its digital
channels but not the terrestrial or the AV1-5 channels, so when I am
watching a DVD or a sports programme via Sky the channel number interferes
with the scoreboard.

I have tried to contact Panasonic customer services but I have been
disappointed with them as they do not reply to emails and their telephone
has a recorded message referring you to the web site or to email them!

Does anyone have any ideas?

Jose