İ dont like icloud 200gb storage and i want refund my money. How?

From https://support.apple.com/en-us/HT207594 ( read the whole page first and you'll find at the bottom of this page):

"* Contact Apple within 14 days of an upgrade for a refund. Partial refunds are available where required by law."

Here's how to downgrade https://support.apple.com/en-us/HT207594