How do I and intern or voluntry work at a modelling agency?

I would like to work at a modelling agency as a model booker but I no if I just send my resume of I probably wont get a call back so I want to do voluntary work or and intern.But Im not sure how to approach the agency.What should I say if they ask me if its for school when its not.Should I call or approach face to face .How long should I do voluntary for.