I'm trying to find a way to store SMS and MMS messages. I need it to also show the person's number so I know who the message is from. Can anyone direct me on how to do that?
You long press any text bubble inside of a conversation to pop open a menu (see image) to click to lock that text in place and/or copy to SIM (which has very limited capacity).
Locking them just requires an extra step when deleting threads so those "locked" text bubbles will persist through a normal thread delete. They'll vanish in a factory reset as well.
Saving to SIM or external SD (via an app) will store them pretty much indefinitely.