Here is the question: Did you buy a refurb from T-Mobile off the website or did you send in a malfunctioning unit and they sent you a refurb. Makes a huge difference. If you sent back a broken
G2X then you should have kept the back cover off your original unit and placed it on the refurb when it arrived. Refurbs never come with a back cover. They will always tell you to return your broken unit BUT... keep your back cover. If you purchased a refurb directly from the T-Mobile site then you need to get with Customer Service and have them send you a back cover. You can also purchase a back cover directly from LG. I had to do that after scratching the clear plastic that protects the camera lens. I believe it was $20 w/free shipping. You just have to call LG USA to order one like I did.
Good luck!