More than a month for correct item delivery??

I placed a R2000 order with Zando and i received the delivery on 11/06/2019. Then one of the items ( a dress i order for a wedding in July) was the incorrect size. I called Zando to collect the dress so that they can send the correct size that i initially order. They came to collect the dress on the 13/06/2019 . According to Zando, the dress only reached them on 19/06/2019. On the 24th of June they sent the 'correct sized'dress. Once again the dress was delivered but once again it was the wrong size ( delivery date 27/06/2019). I once again called Zando to come and collect the incorrect dress which they collected on 01/07/2019. I started calling Zando on 08/07/2019 to find out when they will send the correct dress as i need it by the 20th where i got told that the dress has not reached Zando yet. I called every day after that where i got the same response?? This is a +- R 850 dress and its just missing??? i need that dress before the weekend?? the original order was placed more than a month ago and i still haven't got the correct item?? The call centre keeps telling me that they are waiting for feedback from the couriers but noone gets back to me. They dont even bother to phone me with an update. This is totally unacceptable!!