Hard to get through too mango

I have a flight booked out of Durban to Jhb on 20th August .As I have an international flight I emailed them to kindly allow me the international baggage allowance.I was told I have to pay so much per kg extra online or so much at check in.I tried to go online website is down I called and held for 50mins only to be cut off.So how do i get this extra baggage do I turn up and pay or is mango going too be kind and allow me an international allowance.