Big problem whit service Apple but need an help!!!!!!!

Hi to all friends i have had a big issue whit Apple assistance ad they refused to repair two dead phones one 6 and one 6s reporting that insiede there arent the orginal main board.
Now i know only two system for see the imei and sn one is in back cover and another on sim reader of main board, but the printed grid of sim reader was missing in both phones, now my question is where they are still able to read the serial or IMEI phones.:confused:
Tanks To all

Ps. don’t wirte on sim tray because on it there is nothing written.