FWIW, assuming there is only one SIM card (as there could be more than one in the X7 to serve different functions, but I don't know for sure) it is apparently located in the Telematic Communication Box (TCB) as seen here:
https://www.newtis.info/tisv2/a/en/g...box/1VnYkbhHXT
This unit is actually located in the roof, and is directly attached to the shark fin antenna. Which means it is a modest PITA to get to as it would most likely require taking down the roof headliner. The TCB is module A231.
https://www.newtis.info/tisv2/a/en/g...sav/1VndKwRzJe