How do I disable call notifications and keep text notifications?

I'm in a Skype group chat where there are group calls multiple times a day which I do not always want to join. So I want to disable those notifications BUT I need to keep notifications for chatting. I chat with some other people on Skype who I do want notifications from whenever they message me.
How do I do this?

I'm using Skype Mobile version 7.46.0.596
Using an LG G4 with Android Marshmallow (6.0)