on blu cell phone vivoXI, the back doesn’t open. The sim card tray goes in the side. Hold phone back side up, try will be on right hand side.you will see a small opening. That is for sim card ejector (cam with phone). i read you can use a needle to. You can buy a replacement at Amazon. Press it in (phone off) and tray will come out.
Good luck
Lenore
'''https://blucellphones.us/how-to-insert-sim-card-on-blu-cell-phone/'''