If the receiver deleted the message from their end you will have to delete the voucher and resend again on your end. Note, you the user only have access to your account and should be able to delete from your end.
To delete the voucher:
Login to your App using your credentials,
Go to menu bar "More" at bottom right of your App ,
Tap "Send Instant Money",
Tap "Manage vouchers",
Then tap on "Beneficiary vouchers"
Then delete the voucher.
Let us know should you experience any issues on this.