android 2.3.5 cant upgrade

[AndroidBleh]

i recently got a htc wildfire s unlocked on ebay,used but verified.i tried to update my *software* and it only updated my apps but not the android version.all apps are fine but my device is still on 2.3.3 when its suppose to be on 2.3.5.

its model number is: HTC-A510a
its also not rooted.

Please Respond As Soon As You Can!