You can use the Standard Bank App to buy prepaid airtime - as well as prepaid electricity, data bundles and SMS bundles:
Follow the below steps on how to Buy airtime or Data
Step 1: Open app
Step 2: Go to the “buy” option
Step 3: Choose your prepaid option
Step 4: Choose your network provider
Step 5: Enter the bundle you want to purchase
Step 6: Enter your cellphone number
Step 7: Review your purchase
Step 8: Confirm and verify your purchase
Step 9 You’re #GoodToGo?