Call ended xt1103 in Brazil. Rádio? Frequency?

need urgent help my xt1103 every time I dial it appears "call ended" and then drops the carrier signal when I go on the menu * # * # 4636 # * # * and place "only lte" I can send sms and navigateon the internet but still not make calls, I think the problem is in the band based on the frequency of data, my carrier is VIVO, other operators appears only "no service" already installed customroms and stock in other countries but does not solve, flash other radios and still going, someone can discover what is it? or me through the original radio and baseband nexus 6 xt1103 and how to configure it?... Need a lot of help here in Brazil does not have support for the Nexus 6 :(

VIVO work in 850/1900; 850/1800/1900; 850/900/1800/1900