How to talk to management about schedule issues

I am a new team member that started in the beginning of December and im starting to work service desk as well.

Im not going to lie, I have a lot of personal issues regarding mental health and I am autistic. This is my problem to deal with, and I understand that. I have a very hard time asking people for things and I get really nervous and have a hard time going up to my managers and asking about my schedule.

The issue is I recently started school and I sent in a schedule change form a few weeks before then. The problem is there seems to have been some sort of miscommunication because they started scheduling me like 10 hours more than I was working before now that I am starting school which seems backwards. I cant handle working this much and being a full time student.

What are appropriate ways to contact management? This hasnt really been told to me. Is it okay to call for things like this? Should I ask HR?

Im having a really hard time with this and would really appreciate any advice