Undelivered certificate

I completed my qualifications with UNISA if June/July 2020. Due to covid19 they said our certificates will be courier to us. I waited for my certificate even today. In January 2021 I went to UNISA to enquire about my certificate and I was to my certificate was delivered to me in October 2020 by Skynet and I signed for it. I asked the see the signed document but they didn't show me and they promised to investigate . I waited and they didn't get back to me. In May I went back to UNISA and I was told the same story that they will investigate. I went back again in August and told the same story again. I wrote the email to the Registrar but he didn't respond. Please help me because I need my certificate that I paid for it with my last money and I sacrifice a lot of time studying.