Basically in your world radio transmissions are only possible if traveling through an atmospheric medium. A lot, like sound. Generally, I dislike this concept since radio waves are a form of radiation which does not need a medium, hence why we can observe distant radio waves from far-off stars and other heavenly bodies.
A better option would, in my opinion, be that the atmosphere of your planets have a characteristic that filters or blocks a lot of background radio interference that would otherwise make radio communication outside of the atmosphere very difficult since the interference levels could make broadcasting over radio frequencies limited to only short range.
Since the atmosphere or the lack of one does not permit radio communication, another reasonable way that is relatively in canon with my previous entry; Use either Geostationary sattelites or some way that can stretch a cable out into space and do the information transfer between the surface and out into the close proximity space. From there, if only the radio frequencies are impossible to communicate over, use optical light transmission. This can be done in super simple morse, or more complex Li-Fi The latter, can be used in combination with satellites or other heavenly bodies as extenders that work in the same way as wifi-extenders. This way, you can theoretically attain extreme bandwidth. "Researchers have reached data rates of over 224 Gbit/s". I think I may have solved the issue of getting Earth-Lunar internet as well.