Stolen phone

Try this: go to Google's page about lost devices. Scroll down to 'Remotely find, lock, or erase' and follow its instructions.

Stay away from bullshit apps that are not from Google! Google is the source. Use it.

 

Google's 'Find my phone' service is already included on your phone:
https://www.google.com/android/find
As for those third-party services you're looking into, they need to be installed on your phone and configured, so that's not an issue at this point since you don't have possession of your phone.
Also keep in mind that any remote location app will need your phone to have online connectivity (WiFi or cellular) and Location must be enabled for the above mapping to work. If you had a lock screen enabled whomever has your phone might not even be able to use your phone, so WiFi might not be a likely option since the WiFi networks you have saved are probably well out of range and cellular might not work out if your carrier has already cancelled that account.

Change all your password to all your online services now. You want to keep your email and social media accounts safe. Your carrier referring to the phone's IMEI is only pertaining to the phone's hardware identifier. Once that phone is blacklisted, the other carriers follow that blacklist so getting phone service will be a problem with that phone. But all the apps you had set up on that phone are you're responsibility, or more importantly all you online accounts that those apps connect to. Change your passwords so those apps lose their access.