The title says it all, this has been an occasional problem even back with Pinephone but is far worse now. Some days I cant dial out at all without reverting to 3G service which will be ending soon.
I cant be sure but it appears that I am receiving all/most incoming calls and SMSs; data is working fine too.
A sure way to fix the issue was to hardware switch the modem or even soft reboot it on the Pine, but that is not working now and I am having to use my Nokia 4g candybar phone to dial out.
Which mobile service provider?
golantelecom
Do they approve the BM818 modem for VoLTE?
as far as I have seen there is no approved or banned list, is thisnormal in the EU vs US? I used to just run 3g most of the time to avoid occasional issues since maybe 2018 when I got a pinephone as the net speed was similar, but was still using a (2-3G)N900 and a tethered tablet for web until the N900 SIM-death hit about 2020 before COVID-19 and I switched to the pine. I started to force 4g in the last year especially after I dropped pine64 for Purism since they are shutting down 2g/3g next year. I had a ticket open too but I was able to switch kill-reboot and there was never a good reason for the failure that support or I could track down. This isnew and is only when initiating calls, what log file should I be looking at for failed call inits? Is ther a way to pull modem logs too?
currently looking for the mmcli command to pull IMEI,(time passes) it is ok per Golan Telecom
Assuming you have BM818 Tool app installed and that it’s indicating a modem firmware dated at least September 2022, that VoLTE is enabled, and that you’ve rebooted at least once after enabling VoLTE, then you could:
see if there is an IMEI compatibility check on their website, input the modem’s IMEI (found in L5 Settings), and discover if it’s definitely approved for service
if not, there are 3rd-party IMEI/provider compatibility checks on the internet
or simply talk to Golan’s customer service to verify and troubleshoot
If compatible, VoLTE should work reliably these days, at least in my experience.
This can be found in main L5 Settings app.
There might be some AT command that can show it, but I’m not sure.
For starters: Tips & Tricks · Wiki · Librem5 / docs / Librem 5 Community Wiki · GitLab
for the most sensible two choices for getting the IMEI. 
Otherwise, read on.
Sure.
ATI
shows it.
(Untested) Also
AT+CGSN
This might not be 100% reliable i.e. across all cellular modem makes and models - because this displays the serial number and there may not be a hard requirement that the IMEI be reported as the serial number.
The links in that page, for example
https://cloud.puri.sm/s/MGt4gkqW5wDMK42
are not valid anymore and none of my Puri.sm accounts
purism@pureos:~$ pass search puri.sm
Search Terms: puri.sm
└── web
├── forums.puri.sm
├── puri.sm
└── source.puri.sm
is valid for https://cloud.puri.sm 
@JCS Did cloud.puri.sm get reorganised out of existence?
Any official, relevant BM manual should probably just be hosted within docs.puri.sm
FWIW I just pulled the IMEI form the modem settings, but there used to be a better compilation of MMCLI commands. One thing Pinephone had over purism was the modem was pretty thouroughly hacked, as in 80% foss android code 20% blobby stuff, otoh I did a firmware update and borked my brand new replacement PPpro system board’s modem and pine64 gave me the finger, told me to goto forums when I was the forum modem guy and closed the ticket.
I’ve mailed support@ The ticket number is #14553, if someone wants to attach to it.
I was answering this question, though:
There’s always this as a starting point:
purism@pureos:~$ mmcli --help
Usage:
mmcli [OPTION…] - Control and monitor the ModemManager
Help Options:
-h, --help Show help options
--help-all Show all help options
--help-manager Show manager options
--help-common Show common options
--help-modem Show modem options
--help-3gpp Show 3GPP related options
--help-3gpp-profile-manager Show 3GPP profile management related options
--help-3gpp-ussd Show 3GPP USSD related options
--help-cdma Show CDMA related options
--help-simple Show Simple options
--help-location Show Location options
--help-messaging Show Messaging options
--help-voice Show Voice options
--help-time Show Time options
--help-firmware Show Firmware options
--help-sar Show SAR options
--help-signal Show Signal options
--help-oma Show OMA options
--help-sim Show SIM options
--help-bearer Show bearer options
--help-sms Show SMS options
--help-call Show call options
--help-test Show test options
Application Options:
-K, --output-keyvalue Run action with machine-friendly key-value output
-J, --output-json Run action with machine-friendly json output
-v, --verbose Run action with verbose logs
-V, --version Print version
-a, --async Use asynchronous methods
--timeout=[SECONDS] Timeout for the operation
purism@pureos:~$
And this: Ubuntu Manpage: mmcli - Control and monitor the ModemManager
In the meantime, here’s a list for a different Broadmobi series: Broadmobi BM806U Series User at Commands V1.0.1 | PDF | Network Socket | Internet Protocols
They possibly apply to the BM818 as well.
And the general operating manual for the BM818 (in PDF form): https://fccid.io/2AON8-BM818/User-Manual/BM818-Coperation-manual-V1-4-4107101.pdf lists a few, but not all AT commands.
A general guide about AT commands: AT commands 2025: Guide cellular for IoT devices
Also: AT Commands
I’ve read through this doc. This is extremely usefull, even more to test a new modem card. Ofc you need this special testboard for this, but I imagine that this is in the market somewhat standard.
Do we know what OS is running on this modem? I remember vxworks was popular back when openwrt was just new. The pine64 modem was a headless android derivative so easy to hack over ADB.
And now today after a few weeks of trouble VoLTE just works again….
Maybe your provider broke something, only recently realised, and just fixed it?