TeelPay makes it convenient to buy airtime for all networks in Kenya. Simply use 4142145, the official PayBill Number to buy airtime for Safaricom, Airtel and Telkom for free. However, for airtime more than 100, MPESA transaction charges apply. 

1. Go to the Lipa Na M-PESA option
2. Select PayBill option
3. Enter the business number, 4142145
4. Enter your phone number as the account number
5. Enter the airtime amount you want to buy
6. Enter your M-PESA PIN and confirm the transaction

You will receive a confirmation message from M-PESA plus a message from the network you are buying airtime for with details of the amount of airtime bought.