How to get rid of "marker"?

I imported a geojson point data and it showed up on the map with a marker. I dont want any marker to be shown, only a label. I see properties for marker-color, marker-size, but even if I don’t see one for getting rid or disabling it, there is a default marker.
How can I get rid of the marker?

After load, iterate the entities and assign each billboard to undefined, i.e. “entity.billboard = undefined;” Since you say you want labels, I assume you are already doing something similar to add the label.