It hasn't happened to me yet. I think context matters and obviously a bit of courtesy. Like a quick, "sorry that was important", or a heads up before like, "my son has a cold" or something. Now me, personally I make sure that hour to two hours are fully free. Because I do NOT check my phone when I'm fucking (go away)! That's just me though, I want to be in the moment. I guess if she was really rude or aloof and on the phone I'd just take the L, leave and never repeat. I wouldn't ask for my money back but I'd want to.