The Pep Boys review: my manager changed my schedual without notifying me of the changes and rude to the employee's

I was scedual to be of on 1/12/2020 but when I got home I took a look at my schedule on the app on my phone and I noticed that my scedual had been changed so I'm trying to find out if my manager can change my scedual without notifying me of the changes and they are very rude to the employee's and they do it right in front of the customers and others