Mijoy cancelled and refuses to refund the full deposit.

I paid a R4000 deposit to Mijoy to reserve a puppy. One became available sooner than expected. We agreed on a slightly discounted price, ( she offered the discount in a voicenote which I still have) and that I would pay the full amount by October. The agreement was confirmed by another R 5000 payment. R4000 there and then on acceptance and another R1000 a week or so later I was so happy with the choice - I named my puppy and got photos and updates on her. Then the breeder changed her mind one Saturday morning, out of the blue. She wanted more money for the same puppy because she was keeping it slightly longer. I did not want to change the deal and so she cancelled. She told me clearly in a voicenote which I also still have: "I think the way forward is for us to call it quits" and she demanded my banking details, which I gave her. I even asked a mediator on the Monday morning to help me save this deal. I really wanted that puppy. According to the mediator the puppy was already sold. Adding insult to injury, I was only refunded R 8500. The breeder feels she is entitled to an admin fee for newsletters and bank costs. even though SHE changed the whole deal. She has still not refunded me the balance and has blocked me from contacting her.