Add alipay for renew billing.
Since the new user can use alipay to make a payment. The old user should get the same convenience too.
The old Credit Card Preapproved Payment is very inconvenient for Chinese users. Cause of the Bank in China will mostly make a phone call to user to confirm payment, when an US dollar payment happened, if the user missed that phone call, the payment will failed.(especially an USA payment maybe happened when a chinese user was sleeping).
So it would be nice if the alipay will be available for old users to renew their account.