This official article from Google will help you cancel your subscription through your Google Account.
Note: You might be logged into a different Google Account than the one you used to subscribe to. Make sure you're using the same Google Account and go through the steps in the article again.
HUAWEI device (AppGallery store)
If you started your Pro subscription on HUAWEI device (AppGallery store), you can cancel it by taking the following steps.