As the text message APP matters I'm going with "contact the author of the text message app."
If you can replace that text message app with one that can do this, then you fixed it at the source.
You write that apps to save messages don't work so again that's a failure.
Time to change the messaging APP.
Bob
I've switched from a GT-15503T to a GT-I8160L recently and I've been trying to save my text messages between me and my friends to my sim or SD card. I have tried downloading apps which claim to save messages to sims or SDs but those don't work. I've also tried advice from other forums which say that if you hold down on the message you will get a prompt to save text messages to sim but even if I have both sim and sd in that prompt doesn't come up. Can someone please help?

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