@rockhopper ...
That depends on the level of support your school has selected. For some schools, they pay Instructure (the folks that make Canvas) for Help Desk support. So, instructors, students, and local Canvas administrators at the school can call Instructure directly to get technical support. Other schools have a local help desk staff. Some schools (and mine is an example of this) have a few assigned Canvas administrators that can contact the Canvas Help Desk staff on an instructor's/student's behalf. If you are using the Free For Teacher version of Canvas (not a paid Canvas account), then most support is through the forums here. If your school has a paid Canvas account and has chosen to let Instructure's Help Desk staff handle all support calls, then your school would normally get a unique telephone number to call. But, I wouldn't know what that is.
Here's a couple Guides I can provide you to look at:
I hope some or all of this info will be useful to you.
