I'm somewhat spoilt by the fact that I have played with my two of bandmates, on and off, for over 30 years.
The fact that you had to book a diary slot a week ahead sounded alarm bells for me, never mind the fact he wasn't available and didn't call you back.
Now, it's perfectly possible that B has already sensed their number is up and thinks you're the person that has been tasked with doing the firing and is either in denial or making like difficult.
This is why bands hire a manager. Or because, like us, they're rubbish at booking gigs.