128 texts show up a) when you receive a voicemail notification and b) when you call your voicemail.
Text 2300 is a little more general and will show up when:
- You receive a picture / screenshot / GIF
- You send a picture / screenshot / GIF to another T-Mobile user or
- You were part of a group message and photos / screenshots / GIFs were shared or somebody reacted to a message or photo (for example - “Liked a comment or photo”).
This started happening around July as my guess is there was a system update. Hope this helps!
