I follow a simple trick when I watch these channels.
There is a 'picture size' button on d remote of samsung TVs, put it in 'zoom' mode, and enjoy the chnls in full screen. :k
Increasing only height will distort the picture. I think changing picture size on TV will either distort picture or cut the picture. It may require some kind of hi-end upscaler or need to do something from broadcaster/DTH end.