When you want to have different names for your 2.4G and 5G SSID do the following:
Go to the Wifi Settings:
Click on the Settings for your Wifi:
Now you can see taht your 2.5G and 5G has the same name. Click on the ticked box to separate the SSID (Wifi) for 2.4G and 5G and untick it.
Now you can enter different names for your 2.4G and 5G Wifi and save it: