Re: Wanna buy a Pixel?
Pretty much all mobile phones use the IMEI as the unit, user and phone number master identifier. This usually resides on the SIM.
And yes, reassigning an IMEI number is a real pain in the arse. I know, I used to do this at the enterprise IT level for the phone system repair tech's phones that they use and I had direct access. It wasn't easy even with that much authority and yes, the system recognition of the new equipment assignment is still measured in days. If they were lucky.