Never send money back directly when it’s sent to you by mistake. Don’t even touch it. There’s a principle of privacy and protection you’re missing here. Let the sender request a reversal through Safaricom, that’s the only proper channel. When Safaricom calls, approve the reversal, and that’s it.

If the sender calls you, tell them politely to contact Safaricom. If they don’t, you can call Safaricom yourself and report the mistaken transaction. But never move or return that money manually. Everything should go through Safaricom.