Huawei E353 firmware with voice call feature

[expert_vision]

I googled a lot and after all this time since release I still can't find a firmware update for E353 with voice call feature. My exact model is E353Wu-1 and the current firmware is 11.810.09.40.156_B427, which is the original one. and can be found on internet. However, I can't find any newer one that has voice call feature.
Does anyone have any information regarding a newer firmware for E353 or any tips? How are this firmware updates distributed and why are they found only on unofficial websites?