# Calls use GSM not VoLTE with German carriers - potentially big problem? **URL:** \ **Category:** uConsole\ **Tags:** hardware, 4g\ **Created:** [July 10, 2026, 6:11am UTC](https://forum.clockworkpi.com/t/calls-use-gsm-not-volte-with-german-carriers-potentially-big-problem/22915 "2026-07-10T06:11:44Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![ell1e](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/ell1e/32/17181_2.png) [@ell1e](https://forum.clockworkpi.com/u/ell1e)\ **Post date:** [July 10, 2026, 6:11am UTC](https://forum.clockworkpi.com/t/calls-use-gsm-not-volte-with-german-carriers-potentially-big-problem/22915/1 "2026-07-10T06:11:44Z")
Hi, I help postmarketOS users test the ClockworkPi uConsole. They noticed that during calls with the firmware as-is (no firmware updates from the point the device shipped from ClockworkPi to the user) the modem will drop to GSM for calls rather than use VoLTE when using German carriers, checked via `mmcli -m 0` during the call. At the same time, Germany is apparently planning to phase out GSM calls soon, I think in around one and a half years. This seems to mean calls will soon be unavailable unless this is fixed. Therefore, I wanted to report this since there seems to be a problem with the modem, and at the same time ask if there are any official instructions on how to fix this. If there aren’t yet, there probably should be some. ---
**Author:** ![white-round-square](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/white-round-square/32/10385_2.png) [@white-round-square](https://forum.clockworkpi.com/u/white-round-square)\ **Post date:** [July 10, 2026, 7:58am UTC](https://forum.clockworkpi.com/t/calls-use-gsm-not-volte-with-german-carriers-potentially-big-problem/22915/2 "2026-07-10T07:58:22Z")
there is a firmware update, not sure what it does though > ---
**Author:** ![ell1e](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/ell1e/32/17181_2.png) [@ell1e](https://forum.clockworkpi.com/u/ell1e)\ **Post date:** [July 11, 2026, 8:44am UTC](https://forum.clockworkpi.com/t/calls-use-gsm-not-volte-with-german-carriers-potentially-big-problem/22915/3 "2026-07-11T08:44:33Z")
The 4G internet reportedly no longer works after the upgrade. Seems like the `cdc-wdm0` gets replaced by a `ttyUSB2` device in the `nmcli` listing, and attempting to bring it up results in this: ```plaintext # nmcli device up ttyUSB2 Error: Connection activation failed: PPP service failed to start. ``` This seems to happen despite `mmcli -m 0` showing a `registered` state with access tech “lte”. ---
**Author:** ![ell1e](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/ell1e/32/17181_2.png) [@ell1e](https://forum.clockworkpi.com/u/ell1e)\ **Post date:** [July 11, 2026, 3:53pm UTC](https://forum.clockworkpi.com/t/calls-use-gsm-not-volte-with-german-carriers-potentially-big-problem/22915/5 "2026-07-11T15:53:04Z")
> **[Linux may be dropping RNDIS. Do we have another option of USB tethering?](https://forum.sailfishos.org/t/linux-may-be-dropping-rndis-do-we-have-another-option-of-usb-tethering/21811)** > > As there is a discussion of dropping the RNDIS driver from Linux kernel, and all of us Linux users probably need it to tether our SailfishOS devices over USB. Could the system adopt another USB-Ethernet layer in a future release? Or is this... I think this could be why. So is the new firmware only compatible with rndis? Since that seems to mean that it may no longer work on any newer Linux device in the future and it’s a dead end. But so is non-VoLTE 2G calling that appears to currently be used by the modem for e.g. “O2 Germany”. So the situation looks concerning, as far as I can tell. I wonder whether ClockworkPi is aware of this development? But perhaps I’m missing something. ---
**Author:** ![white-round-square](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/white-round-square/32/10385_2.png) [@white-round-square](https://forum.clockworkpi.com/u/white-round-square)\ **Post date:** [July 11, 2026, 7:43pm UTC](https://forum.clockworkpi.com/t/calls-use-gsm-not-volte-with-german-carriers-potentially-big-problem/22915/6 "2026-07-11T19:43:42Z")
you are digging deep!