ok, try one last thing. Go here
http://live.xbox.comLogin using the LiveID you used for your phone... you might be asked to create a GamerTag, do so.
Now in the upper right hand corner of the page, you'll see your login information.
- Click on Add Points
- Select the least amount of points and then click NEXT.
- You'll be brought to a payment screen asking you about payment type.
- Add a new Credit Card.
- LIE about your address, Google a Singapore address and use it, but keep your name, and other credit card information legit.
- Click on SAVE, if your card gets validated you'll see it on the list of credit cards. If not it'll complain about failure to validate.
- Once validated DO NOT complete the purchase of the Microsoft Points obviously, once you have a card in your account it'll be accesible by your phone.
This actually works! I was able to purchase apps now and renew xbox if needed. Thanks!