If you haven’t already, you’ll need to buy a Safaricom SIM card for your unlocked mobile phone. You can get these at the airport or in Mumias, and will need to have a form of identification with you when you go to buy one.
Once the SIM card has been activated on your phone, you can ‘top up’ your credit by buying a Safaricom scratch card/s. These are available in 10KSH – 1000KSH amounts – smaller amounts can be purchased in Musanda, for larger amounts you will need to go to one of the supermarkets in Mumias.
Local calls to Kenyan mobiles are very cheap. A text/SMS message costs 2KSH. Calls to UK landlines cost about 1000KSH per hour (dialling code +44 for England, +254 for Kenya).
Typing *144# will show you your remaining balance.