The OP's complaint, as I understand it, is that BA attempted to use a method of communication which requires a third-party app that some don't want to use, or do use it but only socially. BA made no effort to ask whether it was a valid contact method. Maybe next they'll send messages over Signal or Telegram or Mastodon or Bluesky ...

This wastes time. BA send a message that isn't received. It could be time critical but instead they just fire it off randomly before waiting for that to fail then using the communication method they should (email or - if mobile number provided - sms).

I personally don't mind WhatsApp. Worse is the fact this forum is full of advice that to get BA to do anything one must use X. That's one app / service I'll never use.