If you lost your phone, but did not setup some tracking program initially, you will want to contact your provider to see if they have any options for you (like replacement under insurance).

Any time your cell phone Is lost or stolen, always call your cell phone provider to immediately suspend service temporarily so ensure that if someone finds the phone, they can't make international calls, texts, 411 calls, data charges, or downloads. If that happens, you are fully responsible for all the charges, except residents in California. If you're in California and have charges on your bill from when the phone is lost, you need to file a police report about the incident and file an investigation. Then they decide whether to waive charges or keep them depending on what they discover. If you installed a GPS tracker, then you can track it from there website. If not, there is no way to find it. Good luck.

Provide your IMEI number to your service provider and wait and watch, since the phone would be useless after that, there are chances your phone might be recovered.