When looking for your Office 365 admin to contact an agent on your behalf, reset your password, delete an account, or do other tasks, here's who you should contact:
Universities and schools: Contact your technical support team. At universities or colleges, usually you can find a link on your university site.
At other schools, there may be just a couple technical people who have admin permissions. Try asking your teacher or school administrators for where you should go to get technical help.
Large businesses: Contact your internal help desk / technical support.
Small businesses: Contact the business owner / co-owner. Often they give admin permissions to their IT consultant who does all the computer maintenance work for their business.
By default, the person who signs up for and buys an Office 365 for business subscription gets admin permissions. That person can assign admin permissions to other people to help them manage Office 365 for their organization.
If you have no idea who to contact at your work or school for help, try asking the person who gave you your Office 365 user account and password.