So you have a single MOV file that has text, like lower thirds or subtitles, basically "burned into" the file, right?
Then you can't edit it...it's part of the movie. It's "flattened" to use a photoshop term...it's part of the movie. There's no way to change the text, or remove it. This is one of the reasons projects I work on deliver a texted and textless version...so if you need to change text, or add it somewhere else, or make it in a foreign language, you can. Import the file, add your own text layer.
Nothing you can do short of blowing up and reformatting the image to get rid of the text. but then you are affecting video quality,and losing a good portion of your image.