163 E-mail sent by mobile phone for verification. Is it only a short message fee to upgrade to unlimited capacity? Will you be tied to any business and charge you some fees every month?

Only short message fee is charged. One of my classmates upgraded to unlimited capacity. But I didn't upgrade. It's 3G now, so there shouldn't be enough space. There is nothing you can do to charge later, because it has passed your verification, just like Fetion.

I suggest you don't upgrade, it's safer.