Q: What to do if the journal is not responding to my withdrawal email for a submitted paper?

Detailed Question -

I have informed the journal of my decision of withdraw my paper a few months back but the journal had not responded. My submission is still showing on the portal as "under review."

2 Answers to this question
Answer: Try to get a notice from them that they are in the process of removing it from their data base and with that you can continue, having that as a proof.
Answer:

Since you have already informed the journal and they have neither responded to you nor taken the paper down, you should send a final email to the journal. Mention clearly that since you failed to get a response from the journal (mention the details of the email that you had sent) and a confirmation of withdrawal, you are considering your manuscript "unsubmitted" from this journal. Once you have sent this email, you can submit your paper to another journal. However, make sure you preserve a copy of all your emails/fax to the previous journal. In case there is any problem in the future, you can always produce these documents as evidence of your efforts to contact the journal.

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What can I do if the journal is not responding since eight months?