At&t data-only sim card registers as 4G network in LEMFO LEMT, 3G network on Kospet Optimus 2

I have two AT&T sim cards. One sim card is a data-only plan and the other is a talk/text/data plan. Both devices use a nano sim card. The talk/text/data is currently my primary phone. In my old LEMFO LEMT, I tried to insert the data-only and the sim card worked in LEMFO, it registered as a 4G network, mobile data works without any tweaking of settings.

However, when I insert the data-only sim into the Kospet Optimus 2, the network shows as 3G. In the settings, the sim card shows - “In-Service” Mobile Network “Disconnected” I inserted my primary devices’ talk/text/data sim card to make sure it wasn’t an issue with AT&T, but it actually registers as 4G network, Mobile Data shows as “In-Service” Status “Connected”, (I can make calls, surf web, send and receive SMS, etc.)

I find it odd the data-only sim card works in the older Android 7.1 device but does work in Android 10. Are there any GSM settings I need to change? Is it a firmware issue? I’m running the latest firmware. Any suggestions would be helpful.

The only settings I’m aware of are in: Settings / Network & Internet / Mobile Network / Preferred Network. Ensure 4G is selected. Also, ensure you’ve got the right Access Point as it may require manual set up.

Failing the above, I would try a T-Mobile sim as AT&T can be kinda particular. Hope that helps.