Network Usage

We have a bonded T-1 with a 3mb/s capacity. I called out ISP and found that 2.2mb/s (1.1 on each T-1) is in use.

Unless someone here is downloading and/or streaming music 24 hours a day, something’s not right here.

Does anyone know an easy (and inexpensive) method of figuring out our where our bandwidth usage is coming from?