I don't think you are overreacting but

(1) re whether the session on: that has been my experience. If you don't hear from T, then yes, assume the session is on. I would be the one to reach out and check with T (in circumstances you mention) to be sure the session was going ahead. So, if T doesn't cancel, the session is on.

(2) re being charged: again some Ts will charge regardless if you don't give their them the stipulated notice in the contract you both signed before working together. Again, some Ts will apply the boundary regardless of length of time they have known you or whatever circumstances arise.

Your feelings are valid but this is how some Ts operate. It is a business after all and some will apply the 'rules' regardless.