There is, it is by the escalators from the Pallasades near the ticket barriers and near a WH Smiths.
If you're coming from the New Street (the old Victoria Square one) it's dead ahead or left and then ahead.
It's unusual because they use a ticketing system to determine who is going to be seen a la Argos and there seems to be an emphasis on using the machines the majority of which are next to the ticket office. This is not to be confused with the Network West Midlands shop/info centre (but you can buy daytrippers from there)