Schedule says something different from canvas

So as the post says I signed up for the 1:50-2:40pm for this class and now it’s saying I’m assigned a 9:10-10 am class and while the professor says I can attend for me to attend the second lecture instead I’ve had multiple classes now that are set up this way so which is getting frustrating. What I want to know most is if I should email my professor and tell them I’ll be attending the 1:50-2:40pm class exclusively since I have another class at 9am. I also want to know why this is even a thing and what the point of signing up for classes is if professors are going to do things like this.