Dentist Cancellation Fee for Flu?

Just wondering peoples thoughts on this, I had a dentist appointment last week and texted them the day before letting them know I was sick and didn’t want to get anyone else sick. They never responded. I then get charged a $100 fee for not canceling 48 hours in advance.

Anyone who has had the flu knows it’s often a sudden onset with no warning. I told them this and they said the “system” automatically applies the late cancellation fee. It sounds like I should’ve just gone in for the appointment even when I was sick.

Is this just a business being shitty business in Los Angeles or do I just need to take the blame on this one?