If you're using the Messages app on an iPhone, you can unsend a message by following these steps:
- Open the Messages app and find the conversation containing the message you want to unsend.
- Tap and hold the message you want to unsend.
- Tap "More" from the pop-up menu that appears.
- Select the message(s) you want to delete by tapping the circle to the left of each message.
- Tap the trash can icon in the lower left corner.
- Tap "Delete Message" to confirm.
Keep in mind that this only works for messages that have not yet been read by the recipient. If the message has already been read, you won't be able to unsend it. Additionally, if you and the recipient are using iMessage, you can also try to use the "Delete for Everyone" feature, which will remove the message from both your device and the recipient's device. However, this feature only works if both devices are running iOS 12.3 or later, and both devices have the "Send Read Receipts" feature turned on.