Head to the 'Wallet' tab, then tap the 'Save' banner which will display your Goals account. Here you should see ‘Upcoming Deposits’ in the blue box. Just tap on the 'Upcoming Deposits’ line, and then the three dots in the top right corner and hit ‘Cancel Deposit' in the box that shows up.
Only scheduled transfers can be canceled as they have not left your account yet. Pending transfers cannot be canceled.