Official iodéOS (Brax3) – VoLTE works with Swisscom but not with Fastweb (roaming)

BraX3 iodéOS
1

Hi,
I’m using a Brax3 with the official iodéOS (stock ROM), and I found a VoLTE issue that seems related to carrier configuration.
Setup

Device: Brax3
OS: official iodéOS (stock)
Location: Switzerland
SIM 1: Swisscom
SIM 2: Fastweb (Italy, roaming)

Observations

Swisscom SIM (local):
IMS Registration: Registered
VoLTE: Available
Calls work fine

Fastweb SIM (roaming):

IMS Registration: Not Registered
VoLTE: Unavailable
Incoming calls → busy tone
Outgoing calls → no audio, call drops after \~10 seconds

Cross-test

Same Fastweb SIM works perfectly (VoLTE OK) on a Samsung phone in Switzerland

Interpretation

Hardware supports VoLTE (confirmed with Swisscom)
Fastweb network/SIM is OK
Issue seems related to missing or incomplete carrier config / IMS provisioning for Fastweb on iodéOS, especially in roaming

Questions

Is Fastweb (or similar MVNOs) supported for VoLTE on Brax3?
Are there plans to expand carrier configs?
Is there any way to manually add IMS/carrier profiles?

Thanks!

2

Seems like an APN misconfiguration. If you can find the APN settings for Fastweb on the internet, try setting it up and checking if it will fix the issue.

If you can’t find APN settings, or reconfiguring the APN settings didn’t fix the issue, I would highly recommend to reach out to the carrier directly and ask if they see any issue on their end. They should be able to access logs that gives them the full picture - APN misconfiguration, failed tower connections (if bands are missing), or else.

3

Hi Plamen,

Thanks for your reply.

The apn is ok, internet works, the problem is just voice and just when roaming in Switzerland (voice works in Italy).

The same Fastweb sim card works in a different Samsung phone when roaming in Switzerland.

Swisscom stopped 3G in Switzerland 10 days ago and the problem started.

Looks like IodeOs doesn’t officially support Fastweb.

Do you know if there is a way to expand carrier configs or to manually add IMS/carrier profiles ?

4

Not much to do on your end other than making sure the right APN is set.
I’d recommend reaching out to the carrier to see if they can identify any issue from the logs.