Mango Refuses Vouchers, Cancellation or Change

On Monday I made a booking for my family for the Easter weekend. We wanted to fly to Cape Town. On receiving my confirmation from Mango, I realized my To and From Airports was the wrong way around. Flying from Cape Town instead of Johannesburg. I immediately phone Mango. They said there where no seats available the other way around. Maybe they will give me a voucher. After numerous emails, phone calls, hanging on.... Still no cancellation or vouchers. I can't even change my existing Booking online. In the mean time there has come other seats available the right way around. But I can't seem to get anyone at Mango to help me with this, before the seats is taking. Its like they have my money...now I mean nothing.....