Open the Messages app
Open the conversation with the voice message
Press and hold the voice message
Tap Delete
Tap Delete Message to confirm
To delete multiple messages, tap Edit or More in the conversation
Select the voice messages
Tap the trash icon
Tap Delete Message to confirm
To delete a voice message from the Voice Memos app, open Voice Memos
Tap the recording
Tap the More button
Tap Delete
Confirm deletion