Wouldn't that actually help? As another commenter said, some apps actually allow blocking random callers. So, presumably, such an app could be used instead of WhatsApp while still being able to contact people on that network. Kind of like in the '00s, when you could use pidgin or some other third-party app to avoid the annoyances of msn or yahoo messenger.
Now it's starting to get worse and worse.
I block SMS notifications since I only get spam there (I'm Brazilian, SMS is basically dead here)