By default, dual-band routers will issue two SSID names, such as: "XXXX_2.4G", "XXXX_5G"，if you select the "XXXX_2.4G", it means your phone is connecting to 2.4G WIFI. (Non-dual-band routers will not have two SSIDs); If you have manually modified the default SSID of the router before, please check the router setting to determine which SSID corresponds to 2.4G WIFI.