As I said in a previous thread you started, there are services you can use to do that, but the phone has to be registered with them. I also gave you a link to two such services. Besides these, there's nothing else the likes of you and me can do.
Even if you are able to register the phone by either sim or IMEI with one of these services, if the sim or IMEI have been changed, then it's to all intents a different phone anyway as far as tracking it is concerned.