Sleepliner invalid advertising.

I tried to book a seat on the Sleepliner bus from Durban to Bellville only to discover that I cannot book in advance in the bottom of the bus via internet. Trying to rectify this via call centre only to find that it is not possible to reserve a seat in the bottom of a Sleepliner since the seats are taken on a first come first serve basis. They should not advertise that seats can be booked exclusively!