What happens if I send money to the wrong WeChat Contact?

You are able to cancel the payment before the WeChat contact accepts. You would need to do the following:

Tapping on the Chat bubble in the chat window
Tapping “Revoke Payment” below the contacts name and contact image.

Please make sure you are selecting the correct WeChat contact to receive the money, because if you make a mistake, and the selected contact accepts the money, it will be too late for you to reverse the transaction without asking that recipient to do so for you.