How do I block it if it's a prepaid account but the phone is a Samsung Note II


Mar 20, 2016
I left my cellphone a Samsung Note II in a rent a car which fetched me from the airport hired by a pharma company but the driver denied there was a phone left in his car but I'm positive it was there because I was still calling my sister in law from there. I got drowsy & probably dozed off so that was the only time my phone went off my grasp then I forgot all about it when I reached home. It took me some time to realize it was missing. By the time the driver was contacted he denied seeing anything.. I was the only passenger & we went straight to Iligan from Laguindingan Airport.
Now I want to disable it using my IMEI, but it's a prepaid account. Do I still go to the service provider?