Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hi Hendrik,
Log into your Microsoft account on this link:
https://account.microsoft.com/services/
There, you should find your Microsoft 365 subscription, click the Manage button beside the subscription, and from there, you can cancel the subscription and disable the recurring billing on the subscription, then when the subscription expires, you can take out a new monthly subscription.
Before cancelling the subscription, you should be entitled to a refund, but not all cancellations result in a refund, you can check your eligibility to a refund using the steps on this link.