WebService, read list of Queues

[grunge]

Hia everybody
I'm new to OTRS i know close to nothing.

I would like to create a bug report page for our teachers.
We have user authentication, php and i would like to use WebService, Soap to create a Ticket.
Creating the Ticket seems to be straightforward and easy.
But...
How do i read the list of the existing Queues from the Webservice, to create a Dropdown-List where the "Customer" can choose the matching queue?

Greetings and Thanks
Philipp