Can't make/receive calls?? Not necessarily a network problem!

[Decembersangel]

There are a LOT of customers posting in the Community that are having problems making/receiving calls on their device even though it has the 'capablility' of connecting to VoLTE/4G Calling and WiFi Calling.
Even if your device is on the SMARTY 'Approved Phones' list (or not) this may not be down to SMARTY supporting your phone BUT  because of something you may not know about.
What many people do NOT know, is that when a mobile phone is sold by a 'Network' it is controlled by them with regards to software/firmware updates that will enable certain features to be available on your phone (even when 'update software' is performed on the device).
I recently got a 'hand-me-down' Samsung Galaxy J4+ phone from my sister that had VoLTE and WiFI Calling ability (among many other features) available to use but they could NOT be accessed on the SMARTY or iD  network.
After much research I found iD Mobile supported my phone and yet when I changed over to their network I was still was unable to  access these features (VoLTE/WiFi Calling) on my device.
What I didn't know is that all phones are controlled by the 'Network' that it was originally sold by and it had their firmware enbedded in to the device
For example. the firmware on my SG J4+ was:- SAOMC_SM-J415FN_OVF_VOD_PP_0015 / 40009a7d / VOD/VOD/VOD which shows that the firmware on my phone was controlled by Vodafone (VOD) which was the network that my sister was a customer of and had purchased the phone from. 
(This information can be found in the phone under 'Software Information').
Unless I was 'connected to/used' the Vodafone network with this phone I wasn't able to get the firmware updates to enable all the capabilities available.
The ONLY way to 'free' a device for updates, so that it can be used with ALL networks, was to 'FLASH' the phone to an Unbranded firmware.
After Flashing my phone this is the software that is now on my device:- 
SAOMC_SM-J415FN_OXM_XEU_PP_0013 / 40009a7d / XEU/XEU/VOD (XEU is 'unbranded').
I now have ALL the capabilities that this phone has with the capacity to use VoLTE, WiFi Calling etc.
These are the codes to which your phone network is locked in to:-

BTU (unbranded)  
EVR (EE)
BTC, CPW (Carphone Warehouse)
H3G, O2I, O2U (O2)
ORA (Orange)
TMU (T-Mobile)
TSC, VIR, VOD (Vodafone)
XEU (EE & Three)

If you go down the 'Flashing' route... PLEASE do your research! It is easy to do once you know how but there are many things you need to know to do it safely!
SO, the conclusion of this is that this isn't just a 'network provider' problem i.e. unsupported phone, but could most likely be a firmware problem/restriction.
IF, you decide to 'FLASH' a device then PLEASE do your research!  There are many 'small' details to take in to account but once you have all the info it is straight forward and easy to do!
Good luck all and I hope this helps solve a problem that affects so many!

[StuartF_1781577]

Many thanks for your info. Much appreciated, but where start with further research? Anyway thanks again.

[petehal_1316546]

I have the same problem.  But not all mobile phones are sold by a network.   Its perfectly possible to buy a mobile from an independent retailer that can attach to any network.   From then on, yes, that mobile is tied to that network's firmware.   In this case the network is Smarty.   So surely Smarty is responsible for upgrading whatever needs to be done.   Yes?  No?   I feel quite sober at the mo so this does feel like common sense.  Any reactions, pps?   Thanks.

[MSF]

@petehal_1316546 While I do understand your point, I'm not sure that you can expect any network (more so in the case of an MVNO) to cater for every phone. At least Smarty publish an article with a list of phones that won't work and info on how to find out if yours probably will.

I agree that it's hard to understand why each network seems to have a different protocol for VoLTE and wonder why there is no consensus.

[SmartyTrousers]

No, when you buy a phone independently, it is not tied to the firmware of the first network you use. It is using generic firmware from the manufacturer, which may or may not contain a VoLTE configuration for the network you are wanting to use it with.

While Smarty can supply the necessary VoLTE configuration details to the manufacturer, only the manufacturer can get that configuration included in an existing device's firmware by including it in a software update for the device.

Unfortunately, depending on how old your Android device is and how good the manufacturer is at keeping its devices updated, such an update may never come.

It's a little different in the Apple world, where a network only needs to supply Apple with the config and it will be rolled out to virtually every iPhone still in use.