@Jeanette Dehliz Welcome to the Atlassian Community. Sorry that you crash landed here with your first question.
In general, an annual subscription, which is paid in advance, cannot be 'downgraded' to a monthly subscription. You would only be able to change it to monthly at the end of the annual term.
Since you are on Premium, you do have access to Trello Support and I suggest opening a support ticket with them to see if anything can be done for your instance.
https://trello.com/contact#/
Good luck!
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