Good morning Julie,
Apologies for the delay in replying, excursions are ideally to be paid for Rand or US Dollars but ideally South African Rand, both currencies are accepted in South Africa and Zambia, however Zambia operates a closed currency so you cannot purchase these till you are there, however your Tour Manager is highly experienced, always on hand and will guide you all the way though and advise on the best ways to do it.
Are you still yet to receive your final information? Please send me your booking reference and I will look into this immediately.
Thanks
Ben