I can not call fixed numbers when using the standard phone-app.
When I call a number, I hear short the sound that indicates the line is occupied. On the screan I see the message “Call forward conditional is enabled”.
Going to “settings” in the phone-app, under “accounts” I see "fixed numbers >
“enable FDN - fixed numbers are disabled”. To enable FDN I need a PIN2. I don’t know what that PIN2 is, I have just 1 PIN.
My provider told me that they can not solve the problem because it seems to be caused by the hardware or the software.
This is not what FDN does. FDN restricts the numbers you can call to a fixed list of numbers, it does not help you to call fixed numbers.
You should leave FDN off, it is not causing your problem. And, by the way, the PIN2 probably came on the plastic card in which your SIM card was delivered.
In what country are you and what operator do you have?