They may be burned into the video picture rather than as a separate subtitle track.
Why this happens
A separate subtitle track is drawn by the player and can normally be selected or disabled through that player’s supported controls. Burned-in text is already part of the video image, in much the same way as a channel logo or a caption placed by the programme producer. A subtitle switch cannot remove those pixels. The distinction matters when text remains after the player shows that subtitles are disabled, because more language-menu changes will not necessarily affect the picture.
First turn the selectable subtitle track off and look for whether one layer of text disappears while another remains. Some sources can contain both a permanent translation and an optional subtitle track. VideoLAN’s documentation confirms that hardcoded subtitles cannot be disabled as an ordinary track. A different source edition may provide the presentation you prefer, but there is no universal player setting that can reconstruct the clean image beneath permanently encoded text. Avoid confusing this with a subtitle-position or encoding problem, which involves a separate set of controls.
A useful way to work through it
Disable the selectable subtitle track and observe whether any text layer changes.
Look for permanent text that remains part of every video frame.
Use a different available edition if you need a version without burned-in text.