Just found out TPlink X50-5G can lock the band! wow this feature is not found in many other brands. Now i can lock to 5G band NR78 and will not (hopefully) switch to 4G anymore.  Superb.

****UPDATE****
Nope it doesn't lock the band, it is just for display purpose.  No meaning at all 

I didn't mention that NX510V can lock band

But Deco X50-5G definitely can lock band

But no point to lock band for 5G cause there's only 1 band now

It will only show you the available band to lock onto

When it's on 5G, there's only 1 band available, so there's no point to lock band

However, my band locking and selecting CA combo does work on 4G on Celcom and DiGi. What firmware you use?

There's a separate feature for you to choose 4G or 5G, not the same menu as the band selection.

Edit: It's under the network mode menu where you can choose 5G preferred, 5G only or 4G only. It's working properly for me. Can you try using 5G only and report back?

When I test the router on a SIM card without 5G plan. It does not even connect to the 4G network when 5G only mode is selected.

Feel free to share your finding as I am curious as well.
Contact TP-Link support, cause it's working properly for me on the same firmware.

Wow, that's really strange. Thanks for sharing this with me.

You're on android right? blacktubi on ios base of the reviews

Different settings for android and ios maybe? Cant be right?

Raexim is right

I just checked with some expert on this.

Our current implementation of DNB NSA 5G network will not allow you to do 5G only. 5G NSA will rely on 4G to function properly and in our scenario, it will need B28.

The closest thing is 5G preferred but nothing is stopping DNB's 5G radio from bumping you down to 4G if it thinks your poor 5G coverage is an airtime nuisance to other 5G users.

Locking to 5G only will result to no network at all most of the time. Confirmed this recently.