I am guessing it is undue hardship to produce this. It requires technological know how, perhaps software, and frankly, doesn't seem relevant.
I don't keep my text messages, periodically purging them. I have saved some sweet ones from the kids, but when upgrading phones or iOS, I have lost some of them. Personally, I'd ignore such requests and tell the court you have no idea how to do that.
They can't likely subpoena your phone unless it's a criminal investigation.
"Personal density is directly proportional to temporal bandwidth."