iTunes Match is in fact not related to iCloud: it's purely for storing copies of your music which you did not purchase from the iTunes Store and coasts @24.99 per year.
iCloud itself is free at the basic level of 5GB storage; you can purchase additional storage - additional 10GB, $20 p.a., 20 GB, $40 p.a., 50GB $100 p.a.
iTunes Match will automatically renew your subscription at the end of your 1 year subscription by default. To turn off Auto-Renew:
- Launch iTunes 10.5.1 or later.
- Choose Store > Sign In.
- Enter your Apple ID and password, and click Sign In.
- Choose Store > View My Account. You may be asked to re-enter your Apple ID password.
- In the "iTunes in the Cloud" section, click Turn Off Auto-Renew to the right of iTunes Match.
(information from this page: http://support.apple.com/kb/HT4914)
You can cancel an iCloud storage upgrade within 15 days of buying:
Apple have made this as difficult as possible. However two posters have managed to achieve this. Elizellen was able to use Express Lane to get a refund:
https://discussions.apple.com/thread/4198583?answerId=19323996022#19323996022
However if you use Express Lane may find you cannot proceed without entering a hardware serial number which is still eligible for AppleCare. julia22 managed to find a way round that by phoning them - please see this post:
https://discussions.apple.com/thread/3395953?answerId=16968425022#16968425022
it gives the USA number - if you don't live there you will have to find an equivalent number from the 'Contact Us' link at bottom right of this page.
If it is more than 15 days since you purchased the storage you cannot cancel it for a refund; you can downgrade your plan as from your next renewal date. Please see
http://help.apple.com/icloud/#mmd602084a
and expand 'Downgrade your storage for the next plan year'.