Are you referring to Instant Money voucher? Please ask the receiver to first restart their device and if they still have not received the SMS in 10 minutes, as the sender you can do a reversal to create a new one.
Instant Money VoucherReversal
Tap to your top right corner (Transact)
Select: SendInstant Money.
Select thevoucheryou would like to reverse anddeleteand confirm your transaction by using the pin that was shared with the receiver.