People carry on here as if such mistakes can never happen to them. For one not all the numbers you send money to by Mpesa would be in your phone book. Secondly if it is in your address book it may be a matter of confusing similar surnames or first names. Or you could be sending money under a lot of stress - like someone seriously sick in the hospital. The list is really endless.
It is only sensible for the service provider to ensure that there are checks in place to protect its user and to that end put in place clear dispute resolution guidelines. A good example of that is Paypal where I believe you can cancel a transaction before it is completed or ask for a refund from the recipient within 60 days. They even have avenues for complaints and their resolutions in order to protect both buyers and sellers using their platform. I think there is a time that CBK was talking upon regulations needing to be in place for the protection of mobile money transfer users. I don't know whether they were ever put in place.
@quicksand, you are right about refund if not done well, possibly leading to fraud. However I think Safaricom has a way of handling that. Sometime back I tried to send some guy money by Mpesa only to receive a message that I could not send money to that number. When I called him he told me he had sent about 50k by mistake to a wrong number. He then called Safaricom immediately. What they did was to cancel the transaction but while they investigated (I don't know how) his Mpesa account was suspended such that he could not deposit, withdraw or transfer money using it. I think it was for over 72 hours. Ultimately they were satisfied it was genuine and refunded the money to him.
He who can express in words the ardour of his love, has but little love to express. - Petrach, Son. (That men by various ways arrive at the same end. - Montaigne, The Essays of.)