You should not be charged for Windows Live OneCare at all since it is no longer able to be renewed or sold.
If you have been charged for renewal -
How to reach support (FAQ) - http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90
If you are not referring to Windows Live OneCare, but another Microsoft service, go to https://billing.microsoft.com and select the subscription service to see what contact options are available for you.
-steve
~ Microsoft MVP Windows Live ~ Windows Live OneCare| Live Mesh|MS Security Essentials Forums Moderator ~