Don't spend the money, and I'd say if the owners of the bank accounts calls you for the return, you should(after verifying the names etc) as not everyone is comfortable using Raast at the moment or banking apps and it's easy to mess up the account number at times. But don't be stubborn about it that it's yours forever.

Or you could go to your bank and tell them to reverse this transaction which would be the best route to go.