How to cancel too many prepaid Xbox Live membership?

You'd want 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

How do I cancel a Gold Family Pack membership?

For information about how to cancel your membership, see
Cancel your Xbox LIVE Gold Membership.

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Once the membership has been cancelled or run out you can go to a regular Gold membership.

two things first

1 to remove a creditcared it cannot be on an active membership

2 that being said to remove an creditcard the membership has to be canceled

as long as there is over 1month left on the membership then a prepaid token will be issued

if there is just 1 mnonth left then the membership is canceled

this is why they warn you if there is less amonth left

however

if a prepaid token is issued then what will happen is the membership is canceled immediately and the account will remain silver till you receive a email in 3-4business days with the prepaid token

then you get your gold back

I checked my gold tenure on the link eG x Thee Elf posted and mine says

Prepaid 12M Xbox LIVE Gold this one isn't canceled

Prepaid 12M Xbox LIVE Gold canceled

Prepaid 12M Xbox LIVE Gold canceled

Prepaid 12M Xbox LIVE Gold canceled

gold 1 month free trial canceled

but yet I have no number next to my name

If a prepaid membership card was redeemed on an incorrect account you should contact Xbox Billing Support at 1-800-469-9269 (in the U.S. and Canada) to have them cancel the existing membership and provide you with a new prepaid token.