Straight from the advert:
1. Dial *151*200# to access the EcoCash menu
2. Enter your EcoCash PIN
3. Select option 8 'Pay Bill' option
4. Enter the Biller Code: 22108
5. Enter the amount
6. Enter the account number
7. Please enter month paid for (can only be 1 or 12)
8. Select option 1 to confirm the transaction
9. Select Send option