Can't update android on Cubot x6

I have the same phone as my friend CUBOT X6 MTK6592. But he can't update his android version and don't have option "Wireless update" to do it in "Settings > About phone" like I do.

My android: version 4.4.2, Baseband version: MOLY.WR8.W1215.MD.WG.MP.V35, 2014/05/28

His android: version: 4.2.2, Baseband version: MOLY.WR8.W1215.MD.WG.MP.V21, 2013/11/23

How can he upgrade his android version to 4.4.2?