To retrieve deleted text from iPhone, maybe you can try to use iPhone Data Recovery Software from TunesKit. If you are used to backup data regularly, you can use this tool to recover data from iTunes/iCloud backup files. If not, try to recover deleted text, messages, notes, photos, contacts, calendars, bookmarks, etc from iOS devices in 3 steps. First to choose data recovery mode, second to scan and preview data, third to recover lost data in seconds.
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iOS System Recovery