Read the actual edition name
Amazon says selected Prime Video titles have American Sign Language or British Sign Language interpretation identified in the product title. Its help says that interpretation is part of the title and cannot be turned off. This differs from a selectable caption overlay whose visibility can be changed in a player menu.
Consider an edition-selection mistake
A household may open a signed version when one viewer needs it and later expect a subtitle switch to remove the interpreter for another session. Before changing device accessibility preferences, check the selected product edition. This is a proposed way to identify the issue, not a claim that every title has both signed and unsigned versions available.
Keep the languages specific
ASL and BSL are distinct language options, not generic names for any sign-language presentation. Check the edition offered and the viewer’s actual requirement. A written subtitle language or dubbed soundtrack does not establish that the required signed version exists in the current catalogue.
Use the appropriate next choice
If another edition is wanted, inspect the legitimate service’s available title versions and access labels before selecting it. Do not assume another version is included, free or available in the same territory. If the offered edition is unclear, give Prime Video support the exact product title rather than reporting that every subtitle control is broken because a permanent part of the selected picture remains visible.
Questions, answered
Can the interpreter be toggled off in the documented signed edition?
Amazon says it cannot.
Does every title necessarily have both ASL and BSL versions?
No. Amazon describes selected content and actual offered editions must be checked.