SIM Problems after downgrade to Android 9

I finally suceeded in the downgrade of my Xperia 10 from Android 10 to Android 9. In the End of the tutorial you shall check whether everything is working. My Sim Card can be found. I can unlock the phone with the pin number and they show my sim card with the correct provider. But it shows a wrong phone number and neither phone calls nor mobil data are working. I tried another Android 9 Version on Emma but it did not work either. Has anybody an idea what i can try next? :frowning:

What does this mean? Where?
Phones don’t actually know their on phone number… These that claim to use a special phonebook entry on the SIM-card.

Okay so maybe this is not part of the problem but the real problem is that I have “no service”, so I can do no phone calls and have no mobile data.

Have you tried to put other SIMs in the device?