Mango airline instead of SAA

I booked SAA from King Shaka airport to OR Tambo and struggled to check in online since 15 August 2018. When I got to King Shaka airport by the SAA counter I was told my SAA booking is operated by Mango so I need to fly with Mango. I went to SAA supervisor Mr Ashraf Khan and he told me there’s nothing he can do I need to sort it out with SAA head office. I asked him to call head office and he told me I must call for myself. I asked him for any option to be done but he referred me again to head office. My sister called head office but she was told the ticket is SAA operated by Mango so I must use Mango. So disappointed in SAA after paying a lot for money.