How do I get Back all my tv channels on my Thomson topuptv box?

I have reset my channels on my set top box and can no longer get the 5 terestrial channels, I have tried resetting as per topuptvs web site but this has made no difference to the channels as when I go onto say BBC1 it always says there is no signal this also goes for the other 4 channels I am missing.I have a thomson 250GB set top box