I am straight out of uni and I recently started a new job as a web developer. Outside of my department, there are only about 5 people who actually believe I can help them with their questions face to face, despite the fact I have been helping most of the company through the helpdesk for months.
Whenever they come into my department looking for my manager when he is out, I offer to answer any questions and except for a few people, they always say they'll come back when my manager is here.
How do I get them to believe that I can actually help them despite my young age?