I'm sorry to learn about the problems you're experiencing at the moment, are you or the text sender using any applications to compose / read / send the messages at all? Or are you both using the default text application on the phones?
Is this an issue that seems to be happening with one number or are you getting these incorrect text messages from multiple people?
I had exactly the same issue with garbled texts on an Xpetia L, I'd get texts that were half of what was sent then half of a random text sometimes from months earlier and that had previously been deleted.
I now have a lovely new phone plus a new sim and I've not had any more issues so far, at least not that kind lol, I now have other problems with texts and calls which lead me to believe there are issues with the network now.