Failure to deliver a promised order

I took a free course with Shaw Academy for 4 weeks, After completing the final assessment/ exam I was then requested to pay R500 to get a hard copy of my certificate delivered and that it would get to me after 4 months, this was in August, I haven’t received it and when I reach out they keep telling me that it was delivered to the provided address and that they’d reissue it again but cannot trace it since they’re using a local post office. This is not getting anywhere I just want a refund since I’ll keep doing back and forth.