Cellular for AW s6 in Viet Nam

Hi guys,

I've purchased my very first AW and this is the one that support cellular, mean that I can use it without connect to my iPhone. However, it can't connect to any carriers in Vietnam. I don't know if it was designed so or I did something wrong, need advice in this case, and I wonder when will this function available for my AW, cuz AW SE has already been compatible with Viettel in Vietnam.

Thank guys!