A journal keeps requesting reviews after I have declined any more
If you are in the EU or the service provider operates from the EU, send them another email in which you remind them very kindly of their legal obligations. Sending you spam after you opted out of their mailing lists is illegal under the GDPR. Even not providing easy ways to opt out is an offense.
You can get in touch with the journals Data Protection Officer (DPO), if the editor fails to respond, or directly file a complaint at your national Data Protection Authority (DPA).
You can take also take legal steps, they are outlined here: What should I do if I think that my personal data protection rights haven’t been respected? (European Commission)
An email to the DPO with &quot;GDPR violation&quot; in the title will most likely prompt immediate response and apologies though. Fines are substantial if the company doesn't comply.