We decided to buy sim cards in every country to be able to roam affordable. Planning to spend only one night in Botswana we may decide to use our own phones for emergency and upload new stories once we have bought and registered a sim card in Zambia.
Airtel is available in Sesheke town just beyond the Sesheke border on the way to Livingstone. An Airtel container opposite the Pep Stores shop sold us the sim card as well as airtime vouchers which we converted to data.
We bought the sim card and stood around waiting for it to be registered and able to browse before we left. We were warned that if we left before the sim card is properly registered, one may find that the guy behind the counter forgets to send through the registration, and two days later, when the data is still not available one has to phone the head office and troubleshoot. If not registered, only SMS is available.