enapace was close.
When I typed that I meant the signal fade thing combined with no hand over between 2100 and 800. the signal fade thing has since been explained as a known problem they are working on so we can exclude that.
The problem isn't even that they have put it at a lower priority than 2100.
The problem is it is effectively a completely separate network since you need to completely lose 3G to get on it.
This is reasonably similar to EE phones that are idle hanging onto 3G for dear life even when it's not working anymore and refusing to switch to 2G. Although this is a bit different as active calls will often handover.
They shouldn't have released it until they had SRVCC (to handover an LTE call to a circuit switched network (3G)) but more importantly reverse SRVCC so calls could start on 3G and hand over to 800 when you lost the 3G.
This would need a sensible threshold so both idle and active phones could move both ways without losing communication.

This is almost certainly why EE are taking so long to get VoLTE out.
Their priority will probably be 2600=>1800=>800=>2100 so actually in an area where 800 is fully deployed anyone with a 4G voice handset would never see 2G or 3G again and SRVCC would never be used.

Do we know if VoLTE can be disabled on an iPhone other than turning 4G off altogether?

It can yes saw it on a T-Mobile US handset while back here it is on a Verizon one.

https://i.ytimg.com/vi/N26ly8ZSIOQ/maxresdefault.jpg

That menu was when you could only "Disable 4G", not select the highest band manually. I wonder what the new menu will look like...

Being able to turn it off will have a few implications here.
Turning it off would not only mean you would go back to CSFB but also it would have to disable access to 800.
Unless there is a built in mechanism to do that (I doubt it) then they will have to disable the ability to turn Voice on or off.

I suspect it will be disabled or simply not there at all, why?
Because EE want to as fast as possible get the 1800 power cranked up.
They can only do this when they have more users making calls on 4G than on CS networks.
CSFB will then be switched to 2G (or 2G/3G) but they will want the majority of their smartphone user base on 4G voice and not using 2G before this happens.
Also I suspect they will want to get another 10-15Mhz of that 1800 over to 4G at some point.
This will require a lot less users making calls on 2G.
Hence, you will be forced to use VoLTE. not that that is a bad thing.

I'm just thinking ahead... If there is a technical issue with VoLTE and you want to disable it but still have 4G data with CSFB, surely that should be an option?

Yes, I helped my brother in law enable it on his Verizon iPhone 6 last Christmas. Once enabled the phone no longer fell back to CDMA 3G to make voice calls - and calls between iPhone 6 users on VoLTE were now "HD voice" that the CDMA network couldn't support.

when you enable / disable VoLTE on the Verizon handset there is obviously a dialog between the handset and the network as it takes a couple of minutes to update the screen.

So I would assume if you disable VoLTE the network would stop your IMEI having access to the 800.

I know and I'm right with you on that. I'd thought of that too.
Problem is though, turning off VoLTE would have to also turn off 800 connectivity and I can't see that being a "thing" that is built into the design.
It's more likely you would have to just turn off 4G altogether.
Don't know really, it's a tricky one.
I'm would put money on it being disabled.

Or you could just take the view that if someone specifically goes into the menu and disables VoLTE then that is their decision to disable something that is enabled by default.

I don't understand why there is so much confusion as to how this will behave. Vodafone's 4G network is mainly built on LTE 800 and carries data well enough. They are upgrading masts and adding LTE 2600 in some areas too.

Why would someone need to be banned from LTE 800 if VoLTE is activated?

Vodafone and O2 would not have this exclusion as their core 4G network is on 800. This is for EE/Three who mainly use 1800. To be fair that discussion is off topic for this thread...

There is a "Bar 4G Voice" product that can be added to an EE account so it may have to be done at CS level...

Yeah, apologies. The conversation is actually not relevant on this thread. Brain not working. VO2 will always have an underlying CS voice network so it wouldn't matter if you could or couldn't turn it off. Just me forgetting this point!


Ah, so it could be requested as a permanent thing... possibly.
That doesn't help you in an emergency unless you know you can turn 4G right off and most people don't know this.
I suppose though the chances of having 4G but with no voice would be pretty rare anyway.
Three handsets now have no ability to turn off VoLTE since the last update so d123 says so EE will be the same.
Anyway, off topic and not relevant to the thread.

Surely the same thing applies to turning VoLTE off though? No "normal" person would bother doing such a thing.

It looks like Vodafone VoLTE release is not as imminent as I was expecting. Apple's iOS 9.2 release brought new carrier settings which included the VoLTE options for Three and EE, but not for Vodafone.

Unless they are planning to push a carrier update shortly later. Or start with Android devices first.

The iPhone and Galaxy S6 models will be first. But there's no date when VoLTE is launching for either Vodafone,or EE.