I convinced my friends to switch from Skype to Discord for this reason. I've had a few new groups every day and I would get calls all day long because if someone wanted to play they would call everyone.

I made a Discord group about a month ago and everyone I know is using it. If someone new wants to play, we add it to this group, so everyone is there.

Also we're not annoyed by calls anymore, as you only have to join the voice channel, instead of calling everyone.