Motorola g62 4g Calling / Volte for use in USA

[DougA]

Hello,

I just got my new phone from work (not via O2) which is a Moto G62 5G - which is dual sim.

I aim to use my O2 sim in the second sim slot for personal use and use the phone on trips to the USA. However when I checked the phone there doesn't seem to be a 4G calling option on O2 when the O2 sim is in the second slot. If I put in the primary slot 4G calling does appear - so I guess it's working?

Now I know the phone might not be happy with 4G Calling as when I checked the non business page and put in the IMEI I was told the phone wasn't compatible. 
https://www.o2.co.uk/help/network-coverage-and-international/travelling-to-the-usa

But on an internet search I had originally found this page https://www.o2.co.uk/business/support/international/travelling-to-the-usa-for-business-customers (thinking my employer was still using O2 but they switched to Vodafone)

So my question if anyone can help is two fold.

1) If I swap the sims so O2 is in the primary slot does it matter which sim is which slot as long I can swap between them?
2) If I travel to the USA and just use the O2 sim, while the phone says 4G calling enabled will it actually be working if the IMEI test on that first webpage says it won't? I can't afford to have a non working phone in the USA as I'll need it for everything especially data. The listing on the Business page seems to say it should, but I'm wary.

Sorry for the long story there and for the fact I'm not that great with phone setup!
Hope someone can help explain!

[madasaf1sh · Accepted solution]

@DougA 

It doesnt matter what slot the o2 sim card is in.  As you swap via the menu's on the phone.. 

I would also trust the business pages more than the consumer pages, as they are usually more up to date, it might if your employer still has an enterprise contact then asking them to confirm.. 

Data will still work, its just the likes of AT&T and T-Mobile making changes to their network infrastructure for calls.