Hello there!
To cancel an iCloud subscription, follow these steps:
Cancel iCloud subscription:
1) Go to settings
2) Tap on your name
3) Go to iCloud
4) Tap on 'Manage account storage'
5) Then, tap on 'Edit storage subscription'
6) On the bottom, tap on Downgrade-options
7) Then, tap on the free option of 5gb
Refund:
If you want a refund of the $2,99, then follow these steps:
1) Click on this link (it will guide you to reportaproblem.apple.com)
2) Then tap on 'I want a..', then select 'refund'
3) Give a reason why
4) Submit the request
If the request gets accepted, you can expect your money (depends on your payment type) within a month.
Hope this helps!