I want to delete about three text messages from Google Voice.
How, when I only see the option to delete the entire conversation?
It seems like you can only delete entire conversations, based on this Google Voice issue about deleting SMS messages,
Google Voice is big on the Conversation, or "SMSThread" as we have named it. I do not think it is even possible to delete a specific message out of a conversation or SMSThread, you have to delete the whole thing.
I checked the Google Voice help page but it doesn't say much,
Here's how you can delete a text or voicemail message or a recorded call on the Google Voice website: Select the checkbox to the left of the message or call you want to delete. Click the Delete button at the top of the page.
There might be a workaround. I don't have any Google Voice SMS messages that I can access, in order to be certain (it was mentioned in the first URL above). When Google Voice says delete, it is moving the conversation to the Trash. To really delete the conversation, you have to empty the Trash. Once the whole conversation is in the Trash, you should be able to see the ID associated with each SMS message. That should allow you to delete just the messages you want, then you can undelete the rest of the conversation's messages that you want to keep.
I also noticed a way to count how many text messages you've sent but not deleted using Google Voice, just in case you want to keep a tally.