how to cancel gold status?

Hey there!

You can sign into your
Microsoft Account and click on "Services and Subscriptions" at the top. From there, you should see your Xbox Live Gold subscription and you can cancel it. If, for some reason, that doesn't work, you'll want to
chat with support for further assistance. They're in a better position to help out with billing/account related issues as we don't deal with personal information here on the public facing forums.

Let us know if you need further help!

Suggest you contact a Billing Agent. You can choose Option 1 after finding your country's support line: See
http://tinyurl.com/XBLnumbers ...

but a faster way to speak to an Agent is to go to
http://xbox.com - sign in there if you can - then go to
support.xbox.com/contact-us Click on Request A Call and type in a few lines explaining your issue and you will get called back quicker than if you waited in queue on hold.

You will need to contact phone support in order to speak to billing directly. They are the only ones who can help you with this -
support.xbox.com/contact-us

You are warned when you purchase gold that auto-renewal will be turned on and your subscription will be renewed unless you turn it off. So by purchasing the subscription you did agree to have auto renewal turned on.

Its the second time already I am buying live gold, receieve the letter that I receive the status gold and at once receive the another notice that I have canceled the status.

You should be able to cancel it at http://commerce.microsoft.com If not, you'll need to contact support and speak to billing. 1-800-4my-xbox if you're in the US/Canada or
http://support.xbox.com/contact-us