Flutter firebaseauth - unrecognized selector sent to instance 0x20d326df8

I am trying to add Firebase Phone Authentication in my app but getting error every time when I want to send tel number to firebase. It states that - unrecognized selector sent to instance 0x20d326df8. I am using real IPhone not simulator. Here is the some part of my code:

Expanded(
            child: Align(
              alignment: Alignment.bottomCenter,
              child: Container(
                width: double.infinity,
                height: 60,
                child: ElevatedButton(
                  style: phoneNumber.toString().length > 7
                      ? mainButtonStyle
                      : ElevatedButton.styleFrom(
                          elevation: 1,
                          shape: RoundedRectangleBorder(
                            borderRadius: BorderRadius.all(Radius.circular(10)),
                          ),
                          primary: Colors.orange.shade200),
                  onPressed: () async {
                    FocusManager.instance.primaryFocus!.unfocus();
                    if (phoneController.text.isNotEmpty &&
                        phoneController.text.length > 7) {
                      setState(() {
                        showLoading = true;
                      });

                      await _auth.verifyPhoneNumber(
                        phoneNumber: codeOfGermany + phoneController.text,
                        verificationCompleted: (phoneAuthCredential) async {
                          setState(() {
                            showLoading = false;
                          });
                          //signInWithPhoneAuthCredential(phoneAuthCredential);
                        },
                        verificationFailed: (verificationFailed) async {
                          setState(() {
                            showLoading = false;
                          });

                          print(codeOfGermany + phoneController.text);
                          showSnackBar(
                              context,
                              'Etwas ist schief gelaufen. Bitte überprüfen Sie Ihre Nummer und Verbindung und versuchen Sie es erneut',
                              iconDataForSnackBarInfo,
                              3);
Text(verificationFailed.toString())));
                        },
                        codeSent: (verificationId, resendingToken) async {
                          setState(() {
                            showLoading = false;
                            currentState =
                                MobileVerificationState.SHOW_OTP_FORM_STATE;
                            this.verificationId = verificationId;
                          });
                        },
                        codeAutoRetrievalTimeout: (verificationId) async {},
                      );
                    } else {
                      errorMessage = 'Phone number not included';
                    }
                  },
                  child: Text(
                    "Send",
                    style: buttonTextStyleBlack,
                  ),
                ),
              ),
            ),
          ),

Additionally when I am using in TextFormField - keyboardType: TextInputType.number it gives an error such as: Can't find keyplane that supports type 4 for keyboard iPhone-PortraitTruffle-NumberPad; using 27071_PortraitTruffle_iPhone-Simple-Pad_Default. I removed it and only this error gone. But In thix TextFormField user should add tel number and I need show them only number. 

Your help highly appreciated