Dear Sir, I have lost my IPhone 4S in China. Please, kindly support me to find the location of my IPhone or advice how to block the phone.

In order for a lost iPhone to be located you have to have set 'Find My iPhone' up on it before losing it, and it has to be on, not wiped, and able to connect to a network (how else could it transmit its location) - if any of these conditions is not true then locating it is not possible. You can't use the serial number or IMEI number to locate a phone: the former is only useful to identify it as yours if it turns up, and the latter can be used by most service providers to block it, rendering it useless and preventing anyone from spending your credit.

For information on finding or locking a phone on which Find My Phone has been set up please see this page and the subsequent ones:

http://help.apple.com/icloud/#mm6b1aa045

You can only lock the phone yourself using Find My iPhone, and obviously only if you had set that up in the first place.

If you know the IMEI number you can ask your service provider (the people who provide your mobile contract, not Apple) to block the phone - note that this renders it completely useless and is permanent.

If you haven't set up Find My iPhone and you don't know the IMEI number there is nothing you can do, but you should contact your service provider in the hope that they will find a way to prevent a thief from using your credit on it. You can't stop them taking the SIM card out and using it with another service.