Reset your APN settings You can do this by going to Settings > Mobile network/Dual SIMs & mobile network (> SIM card info and settings > SIM card) > Access point name (APN), or Settings > Network & internet > SIM card & mobile network > SIM card > Access point name (APN).
把你家的Wi-Fi 路由器的channel固定在美国和中国共用的那几个。你可以查https://en.m.wikipedia.org/wiki/List_of_WLAN_channels