Welcome to the Community and thanks for reaching out.
To unlink your Spotify account from a PlayStation account that you don't have access to, you'll need to get in touch with the PlayStation support team via the @AskPlayStation account on Twitter or via the PlayStation support site.
They should be able to remove the link between the PlayStation account and your Spotify account.
Let us know how it goes. We'll be here if you have any further questions.
Help others find this answer and click "Accept as Solution".
If you appreciate my answer, maybe give me a Like.