There are a couple of ways to cancel a payment you make with Apple Cash. Just note that if your recipient accepted the payment, you cannot cancel. You must see in the Cancel Payment option described below to rescind the payment.
Steps To Cancel the payment in the Messages app
1) Open the Wallet app on your device and select the conversation with the payment.
2) You should see the Pending payment in the text message box.
3) Tap the payment and then tap Cancel Payment on the next screen.