Sellers work like this only bro,when I first bought Xperia Sola Sony promised an update to Jellybean as it was running on Ice Cream Sandwich but I never got the update while many devices which costed less than my phone got it,sometimes updates also depend on phone's specification,if a manufacturer can't stabilize the new Android version for a particular device that is an year old so it is better to not give the update,otherwise the user would always be facing lot of problems in his device such as lag,sudden shutdown,battery problems etc