Sailfish in the USA

[marbalf]

I’m going to add my two cents here. Through a quick scroll I didn’t find it, but maybe it was mentioned before, in which case I apologise.

I am presently in the USA. At home, I use an Italian Iliad sim card without any problems.

I bought a prepaid Ultramobile sim card here, which works well for my needs (data and texts; haven’t called yet, but it even registered on VoLTE once, I think).

BUT, if I put them in together, the Iliad card gets “deregistered”, and doesn’t connect anymore, while the Ultra keeps working as before.

The only idea I came up with is that maybe there’s some sort of conflict. Iliad uses AT&T’s network, while Ultra (Walmart’s MVNO) uses T-Mobile. When I try to select SIM1 (Iliad’s) network manually, only T-Mobile shows up.
If I insert only Iliad’s card, AT&T networks show up.

So, maybe two different carriers cannot work in the same phone?

[hackman238]

Here in the USA, only T-Mobile and MVNOs which use the T-Mobile network can register with IMS and enable calls using VoLTE. SMS, MMS and data also work on these networks. SMS, MMS and data work with AT&T and any MVNO that uses AT&T. Keep in mind, both T-Mobile and AT&T maintain white lists for phones. MVNOs are permitted to use their own device whitelists for the most part. Puremobile (AT&T GSM-A) works great for data, SMS and MMS. US Mobile (on the white T-Mobile GSM-T SIM) works great with the Xperia 10 ii and 10 iii for data, SMS, MMS and calling. The Xperia 10 iii has very limited service outside of major metropolitan areas due to lacking support for most GSM-T bands used for service coverage in suburban, rural and indoor locations.