Your device (Phone) will always choose the best connection, however the only way to force it to use only 2.4ghz, will be to disable 5G in your SSID/Wi-Fi network ID, however 5G will no longer be available or eve create two different SSID/Wi-Fi network ID , let me add the steps.
Enable the Radios Signal for the SSID:
1: Access to the Unleashed APP or the via web access to the site
2:If you never access before, or you are no sure about the credentials, try the next bundle:
3:Once you gain access, follow up the next steps to enable 2.4 signal only:
Select the WLAN you want to configure from the Wi-Fi Networks component and click Edit> Advanced Options > Radio Control>Enable WLAN on>choose 2.4 only to enable only that signal to be broadcasted.