Hacked!!! trying to look up Hackers Imie

I was Identity Thefted by 2 people I know. The cops and banks are not helping me much so its up to me to get to do the foot work... I know they got my wifi and ported my cell somehow to took over my Google account. I found this device on my Google thats def not mine and Im pretty sure its one of the thieves. using the find my device I got the IMIE of the phone. But I cant figure out how to look up that IMIE to get any info I can on it. Looking in google play under devices Ive discovered the carrier of teh IMIE is AT&T. Ive never used them, ever for cell service.