deleting videos from iPhone without having them deleted from iCloud

does anyone know hot to delete videos from iPhone without having them deleted from iCloud? anytime i deleted video from my phone to make more room, it deletes from iCloud. i guess i can use an external hard drive. i thought the point of iCloud was to have them at stored in place that wasn't your phone. if its just a place to back things up a hard drive could do that.

thanks