Free nights

I earned a free night on their accommodation bookings. The free night had a specific value which is understandable and you would need to pay in the rest if required. No problem so far. However when I tried to utilise this before it expired (I was booking at Mount Grace in Magaliesburg) they would offer me all the types of accommodation as being available but as soon as I wanted to use the supposed free night value I could only choose the most expensive accommodation. This turned out more expensive than two nights for the accommodation I eventually booked without utilising their domain. I tried a few times to get hold of them but to no avail and the emails I sent went unanswered. I am in the process of booking for an overseas trip later in the yrear and am avoiding using their domain. I think it is poor service and not actually giving you what you are offered.