Not paying back cancellation fees

In June 2018 I booked 6 nights at the Letsatsi Lodge, VanRhynsdorp for a class reunion in August 2018. I paid the full amount R5370. Unfortunately I had to cancel the booking due to unforeseen circumstances . They acknowledged the cancellation and paid back the money minus 20%. This was done on the 28th of June According to their cancellation policy 20% fee is payable if the booking is cancelled 31 days prior to arrival. My booking was cancelled more than 31days prior so they owe me the full amount. After 3 months they are just ignoring my letters, not even explaining why they are not paying back the money. I think this is very bad customer service.