1) HBO [STRIKE]channel[/STRIKE] shows the Rocky movie a lot. (This works if you're only talking about the first film in the franchise. If they show the others on a regular basis, you need "movies".)
2) HBO [STRIKE]keeps showing[/STRIKE] shows it every now and then but I watch it whenever it is on.
Please check my sentences.
A lot and every now and then are not the same.
So, can I say "They keep showing it a lot"?
Don't write HBO channel. If your readers are in a context where HBO is known, just write "HBO". If they aren't, write "the cable channel HBO shows...."