You can activate Wingo via Swisscom Prepaid (one-off 20.-). Complicated, but it worked straight away (without changing anything with the device SIM and with simultaneous ringing). If anyone has the same problem, I proceeded in roughly the same way (Wingo and Pixel 9 Pro XL, I think it works similarly for other mobile phone providers): 1st On PC: ordered Swisscom Prepaid eSIM and start setup with QR code. 2. on smartphone: Scan QR code with camera and set up eSIM 3. on smartphone: Press "Mobile network" in the Watch app and do nothing yet (Swisscom should now be suggested instead of "none") 4. on the PC: order a second SIM from Wingo ("for other watches" selected, takes a few minutes, incl. new registration in my.wingo portal) 5. on PC: Configure Second SIM in my.wingo portal -> QR code should be displayed 6. on smartphone: Press Scan in the Watch app in the "Mobile network" and now scan the Wingo QR code -> activation takes a moment 7. on the PC: Complete the configuration in my.wingo Portal 8. in Settings > Network & Internet > SIM cards > deactivate the Swisscom card again Test with smartphone in flight mode worked, outgoing and incoming calls