Suspended Flight: ***** & Bad customer service

We booked a return ticket through Travelstart on the 25th of July for which we were to go to Cape Town using Mango Airlines and return to Johannesburg on Airlink. They decide to send us an email days before our flight telling us Mango suspended operations and we should fill in a form to claim for a voucher meanwhile they expect we should spend money to book another ticket to go to Cape Town using our own money. I do not understand why we had to spend when Travel Start was paid cash for the entire itinerary and they were to make a plan on how we should go to Cape Town either using another airline or immediately getting our refund. We have no idea when this voucher will come and I do not intend to go to Cape Town anytime soon after this trip. Why should it become my job to sell the voucher to get the cash! I tried to tell the agen to book us with airlink and charge us as if its a round trip then we top up. Yes they would make a loss but these are losses businesses make because the customer comes first, especially where the mistake is on their end.

Secondly, we booked the ticket on the 25th of July 2021. Surely Mango knew operations were being suspended, why was our booking accepted???

I need a refund in cash please. I can't be waiting on Mango because I booked through Travelstart not Mango! I should be under no obligation to travel to Cape Town because I have a voucher, that's covering one way