Terrible single decker Greyhound bus

I booked tickets on the 5th of February from Mosselbay to Carletonville. I booked over the phone, talking with an agent. I specifically asked for seats on the dreamliner as i had a broken foot and really needed that extra space. Instead we got booked on the horrible single decker and even though i booked an extra seat, i had to endure 18hrs of extreme pain and discomfort. This is not acceptable. I did email them after to complain but they only said they have the right to change the busses used. Again not acceptable. That singledecker is so small and tight that there is scarcely breathing space. And omw forget about trying to get to the toilet!! Not again. Ever.