Question [Q] cant get back to stock on ls980

sorry for my english
i just buy a lg g2 sprint and the guy who sell me the cell told me that it was unlocked and it was cause im using it with my telcel sim card in mexico but i just find out that it has a custom rom call rayglobe flex 3.5 android 4.2.2 , and i just found out that sprint cannot be unlocked by code and i found a way to get it simunlock , i want to update to 4.4.2 for that i need to return to stock
i follow instructions exactly i download tot and dll for ls980 but my phone says that is a d802 but the back of my phone says ls980 and is a sprint version but my phone says d802 so when i try to use lgflashtool everything go ok but after waiting for conection says wrong model number or check dll
and i cant return it to stock is there a way to change model number so lgflashtool can be use ?
and kind of new to custom roms and root and stuff
i have twrp recovery
or is there like a custom rom that i could flash without loosing my simunlock?
thanxs i hope you could help me guys