Charged for sleepliner boarded mainliner

Upon a trup from harrismith to bloem. With return trip. Each ticket per person traveling was 600 rand for two people to go and return aswell we ended up spending 2444 rand.... expecting to be on the sleepliner coach...... the trip up was no problem whatsoever.... yet the return trip was a nightmare. R600 and whatever for a mainlinet when u expected a sleepliner. I am a tall woman so for my comfort chose the sleepliner.... legroom... hellooooo!!!!!!!!!! Highly dissapointed....paying doyble for my tickets.....