Only the phone service provider can track a phone using the IMEI number and they will only do this if ordered to do so by a court or some other legal requirement.
The only way you can track a lost or stolen iPhone yourself is if you had a tracking app pre-installed on it.
You should report the loss or theft immediately if you don't have any tracking apps on it, so that it can be deactivated to help prevent anyone using it and potentially running up a large bill for you, and so that you can make a valid claim on any insurance policy which covers the loss. Even if your iPhone does not have its own insurance, many home contents insurance policies will cover the loss of items outside the home, so be sure to check this.
in malaysia our telco industrial not that efficient. Even i lodge a report in order to obtain FRI & submit to the telco provide along requesting them to block the phone thru the IMEI reference.
If you have not already done so, you should also change the passwords to any accounts you had on your iPhone, including the iTunes account password, email passwords, etc.
Only your telco can block your iPhone's IMEI number with their network to prevent someone else from using your lost or stolen iPhone with their network.