Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
I'm sorry that you lost your iPhone. If you have iCloud or Find My iPhone activated on it then you can track it. On your computer, go to www.icloud.com
Then login with your Apple ID or iCloud account you used in your iPhone. Click Find My iPhone button. Then click All Devices, then select your iPhone. This will show the iPhone in the map. If you are unable to track it, then click Lost Mode in there. This will password ***** it and show custom message you want on it. You can also ring it from there even if the ringer is off. It will ring if you ring it from iCloud website.
If you can't find it, then click Erase there. This will erase the iPhone and deactivate it. No one will ever able to use that iPhone without you activate it again.
(Once it is erased, you need to provide your Apple ID and password ***** activate it again)
If you have not enabled the iCloud and Fine My iPhone option on it, then you will not be able to track it unfortunately. It can't also be tracked if it is turned off. But it will be erased the moment it turn on (assuming it is connected to internet). Find my iPhone option is your only hope now.
I'd also recommend to change your email password, AppStore password ***** all other passwords you used on it. So the person who get the iPhone will not be able access your emails or other things that require password.
Note : If the iPhone is passcode or finger print protected, then you don't have to worry about the data on it. The person who get it will not be able to crack the code and open it.
You should also call your carrier network and ask them to disable the services as well as backlist the iPhone.
If you've any questions or would like any additional information information, please don't hesitate to ask
If you are not satisfied with the service I provided, please don't rate me bad or poor or OK. In this case, I will only give you possible methods to track it. If you are not satisfied with my answer, you don't have to rate anything and you can close this page without rating and ignore the rating requests.