Dissapointed with service,unreachable call centre lines

I am dissapointed, disgusted and angry at this airline, call centre does not pick up any calls. I booked flights for my sister and 10 year old daughter successfully and unfortunately my sister got sick and couldn't travel and I tried calling them 7 days before and I couldn't reach them even if I call everyday and hold for 2hours.on the 18th of March I went to the airport counters and they advised me to purchase a new ticket because a minor cant travel alone on the 22ofMarch and I did that. Fast Forward On the 22 of March at OR Tambo airport counter a lady Mamelo Mamelo told me to rebook my daughter's ticket because call centre agents cancelled my daughters ticket and keep a receipt then claim later I had to re book for a R1800 ticket and when I am trying to reach them for this claim they are sending me from pillar to post .I even sent the first booking ref VKKH2C and pictures of the receipts and my complaint ref nr is ***2 . Please help in trying to resolve the matter .I want my R1800 refunded and also a voucher for my sister Nomzamo Qhina who couldn't travel because she was sick and has a sick note to prove.