For iPhone
Go to Settings > Cellular > Tap our SIM/eSIM > Voice & Data > 5G
If you only see 3G or 4G/LTE options, then it means your device does NOT support 5G.
For Android
Each device model may have a different Settings menu, but you can try to go to Settings > Connections > Mobile Networks > Network Mode or try to search Network on your device. Then select the 5G option.
Our 5G service requires your phone to support the following 5G frequency signals: Band n28, n78, n79, and n257. If your phone does not support these, then you may not be able to use the service at all (even 4G) after you change the setting to 5G. Please check the compatibility of your phone before changing.
If you would like to use 5G network option in your SIM card, please read here for further details.