T-shirts out of stock.

I went to fetch my goodie bag for the Avon/Justine iThemba Walkathon on 21 October and was told that my T-shirt size (Small) is out of stock. I got X-large. I was very unhappy and sent a Complaint on their Facebook page. They responded via the Facebook Messenger and said the T-shirts were ****** hence there was a shortage. The message went on to say that I can choose a 2017 T-shirt or 2018 T-shirt plus ticket for the Walk, I must send my details. I sent am email to confirm and was taken back and forth and was eventually told the offer is only for those who did not get T-shirts at all and they can't help me. There is no direct number to contact the organisers and I have the proof on my messenger. I registered for me and my cousin and I was promised we would get compensation. I was one of the first people to register for this Walk and I got a size I did not register and on top of that, they were rude about it. I am very angry at this pathetic service for such a big event and would like answers why I was promised something and then told otherwise!!