I just removed my CC from my XBL Account
Primary Goal: Make sure my brother's account becomes a silver, and doesn't renew.
Secondary Goal: Remove the initial credit card on the account (my mother's) from my account.
I removed my mother's credit card from my Xbox Live Account (Mastaglach820) today. I initially called to make sure my brother's account turned into a silver (he has a 2nd one he would rather use on a day to day). After handling that, I asked to have my mother's CC# removed. Xbox support set the process in motion but had to escalate my issue to another part. They do not have access to the account information (which I guess is good).
The only "issue", really wasn't an issue. They needed the credit card holder to be on the phone to verify everything. Outside of that, everything went smoothly. I just cant order/buy anything for a little bit (just to make sure).
Outcome: It was a complete success. Yes, I have heard those "horror" stories of Xbox Support...but to tell you the truth. The support agents I have come into contact with (multiple ones via the XBox.com forums), ceesar from the UK, as well as Christine (if I remember correctly) at 1800-4MY-XBOX, have all been truly helpful, and have caused no issue.