Refusing to reimburse

I have had to cancel my holiday package with STA for end April due a medical procedure that needs to be done. I have sent through the note from a doctor and explained the reason for cancelling. I had paid a deposit of R3000 which I am now told that I will lose R2000 -WHY? I had not taken out travel insurance as yet as my trip was only 29th April. The consultant, Nerissa (WESTVILLE) , that I have been dealing with has not been getting back to me on email and is shocking to work with.