Travel Start is a total *******

After buying 2x airine tickets in 2020 to travel to London and back for a total value of R24 287. They now want to charge me an extra R33 594 to re-book book the same flights this year. They were the ones who canceled my flights in the first place due to Covid! How is this ok? To buy completely new tickets start at R20 000 - this is insane