I think it is almost certainly Sprint-network only, and apparently refurbished. (The phone listed on Unreal Mobile's site specifies it that way.). I think there were some reviews on Best Buy at one point that mentioned/complained about the less than clear info. It would help a lot if BB would always list the model #, and if they didn't copy and paste generic info across different model variations of the same (named) phone.
I don't believe there ever was an all-carrier version of the LG XCharge. I think there were 2 different 3-carrier versions. (1 missing Sprint, 1 missing VZW.)