How do I trace my stolen Galaxy S5 with IMEI when Sim Card has been changed?

[AC Question]

I have a Samsung account but cannot access it without my Android. How do I block the mobile, AND find the number of the thief who replaced the Sim Card with my IMEI number?

 

[B. Diddy]

Welcome to Android Central! Did you report the phone stolen to your carrier (and to the police a well)? Your carrier will blacklist the phone, making it useless for calls by the thief.