You cannot delete an iPhone text message for both sides after it has been sent as a normal SMS or MMS
You can only delete the message from your own iPhone
If the message was sent with iMessage and both devices are on iOS 16 or later, you can unsend it within 2 minutes
To unsend an iMessage, open Messages
Press and hold the message
Tap Undo Send
If the 2-minute window has passed, you cannot remove it from the other person’s device
You can delete the conversation on your iPhone by opening Messages
Swipe left on the conversation
Tap Delete
If you want the other person to remove it, ask them to delete it manually