False Advertising on Prices

On the 20 May 2020 I purchased flights at R599 one way to Durban for the 2 June 2020,The tickets was available on your website and available due to the country going into level 3 lock down,this is a business travel as I am a essential medical supplier..I then received a email last night with a voucher of the amount I booked my flights for...so I then try to rebook and move meetings to the date of the 11 June 2020 and the Price is R1900 that is almost triple the damn price!! This is not on YOU advertised whilst other airlines stated NO FLIGHTS AVAILABLE so I book and that means I must fly for the amounts I paid initially due to your cancellation not MINE...I expect to fly for the same amount of R599 on the 11 June 2020 this is a ****** rip us ffs!! I expect a reply or someone contacting me ASAP