Ticketline Double Booking

On the 26th of March I used Ster-Kinekor's website to book 4 tickets to go and watch Fast & Furious 7 in IMAX at The Grove shopping center for Friday the 3rd of April at 11:00 AM. After booking my tickets I noticed that the seats were still available on the website... I then contacted Ster-Kinekor's Ticketline twice to confirm my booking and for them to rectify the error to avoid a double booking... The second time I phone I spoke to Unathi and she checked my booking using my reference (***0). She told me that she would lock out the seats and send me my confirmation. When I got to the cinema on the 3rd... no tickets could be found linked to the card that I used to buy the tickets and after giving them the confirmation that I got from Unathi they just gave me another print out showing me the seat numbers... But when we got into the movie other people were in our seats and after the manager checked their tickets I was told that I can't get my seats that I booked because the people in those seats had actual tickets and that my print out wasn't valid as a ticket... The movie was also fully booked for the whole day. Therefor I would like a full refund of my tickets....