Assuming it’s an Android phone, tap on Settings >> Network & internet >> Mobile Network >> Preferred Network type. You should see all the Mobile Network technologies supported such as 2G, 3G, 4G and 5G. If 5G is listed, then your phone supports it .
Read moreHow do you know when 5G is ready?
Go to Settings > Cellular > Cellular Data Options. If you see this screen, your device has 5G activated . If you don’t see this screen, contact your carrier to confirm that your plan supports 5G.
Read more