Carriers that work?
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Following the T-mo decision to arbitrarily kill off all new voice service activation for Note 4s in Jan. 2021, I'd love to have some detailed information on what carrier or MVNO and what type of SIM card people are using.
One user already posted that a new pre-paid sim card with AT&T worked with the Note 4 (though at the time of this post the port doesn't have completely audio call capability).
I used Ting.com for my own service while the family used Sprint. Ting no longer can activate the Note 4 due to the T-mo merger (their parent network).
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@clessley the issue is that LTE networks were rolled out for data usage while 3G networks remained in use for calls and SMS, but now, US carriers are dropping support for 3G networks (T-Mobile 01/2021, AT&T 02/2022), and thereby phones which use circuit-switched fallback.
Early LTE devices have used LTE frequency bands for data transfer, but "fall back" to 3G UMTS frequency bands for calls and SMS. This was provisioned for since LTE doesn't support circuit-switched calls, and this is why you can't use data on older phones while making a call.
I've used a Nexus 5 since last September, but it got water-damaged so I bought a Oneplus One. When I switched SIM cards, my AT&T account got suspended: they have done this since January as part of a phase-out leading up to 02/2022.
I believe the solution is to purchase a phone which is compliant with LTE Category 6, or above, since it will use the IMS services necessary for supporting VoLTE (T-Mobile) and HD Voice (AT&T).
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@formula82 Well that's half of the story, sadly. IMS support is a pure proprietary vendor implementation, and Ubuntu Touch has no access to it currently. Also, every vendor, and probably every phone, needs a specific solution that involves hacking and reverse-engineering code where we do not have the sources for. There is currently no UT device that supports LTE.
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I'm using Straight Talk on AT&T network for now with my OnePlus One. Have also been using same SIM with a couple of Xperiae running SFOS X. So far so good. It'd be a shame if voice support disappeared or phone stopped working in near future. Guess I'd either get a flip phone or go old school -- land line and answering machine maybe.
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@Flohack thanks for the clarification. Is there any minimum requirement on the LTE UE category, or is the main roadblock the IMS support at the software/firmware level?
@robthebold fwiw, AT&T said my service would have continued uninterrupted through 02/2022 if I hadn't swapped the SIM
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@formula82 No the roadblock is entirely the IMS subsystem, the handling of the SIP audio streams, dialling etc.
