Booking Error by First Resorts leave me Out of Pocket

I was booked into a 6 sleeper unit when I requested accommodation for 7 (3 adults and 4 kids ages 7 and 9) via the call centre. At the time of booking I was advised by the agent that she would speak to management to swap me into a larger unit. Despite repeated messages, mails and calls I did not get feedback on the status of that request. On the day of checkin we decided to go through earlier however I was not allowed access I was told that I need to book an extra unit for the extra person. I refused as the error was entirely the fault of First Resorts. The supervisor eventually acquiesced and i was made to pay R 500 for the extra person for our stay. The supervisor said he'd log my complaint but that was not done. I have requested a refund of that amount and have repeatedly been told that they are retrieving the call with the agent. I am constantly following up with no sense of urgency on the part of management. I am very disappointed.