If I switch from monthly to annual subscription in middle of month, do I get credit for unused subscription period?

Hi there jaykayaz,

We understand you're asking if you'll be partially credited when canceling a subscription before the subscription period ends. We're glad you've joined us in Apple Support Communities, and we can provide some guidance.

"If you cancel a paid subscription, you can keep using the subscription until the next billing date." Have a look at the 'About canceling subscriptions from Apple' section of the related article linked in blue at the top left corner of this page for more information.

With that said, you could try requesting a refund by following the steps in this support article:

Request a refund for apps or content that you bought from Apple

We hope this information is helpful. Don’t hesitate to let us know if you have any more questions.

Take care.