Xiaomi 4 can't call, can't talk, how to do

M4 Telecom 4G version of the brush autumn 5.1.1 appeared a problem with 4G network but can not communicate, I do not know if friends with Xiaomi 4 have a similar problem, the following Xiaobian will share for you Xiaomi 4 can not talk Solution 1, first brush into the bottom of the latest development version of MIUI! Then brush into the autumn bag. This will not say, after brushing, you will find 4g network, but you can't call. Enter the dialing interface input *#*#4636#*#* will automatically enter the test mode
2, then set the preferred network type to select LTE GSM CDMA, then click to close the wireless network and then click to open 3, if not, Click smsc refresh in the figure below, then click update, repeat the above steps