Problems in getting IMEI and Operator Name

Question

i am developing an app and needed to handle the Telephonymanager, however, every time I use it gives some problem. For example:

E/Mplugin: Unsupported class: com.mediatek.common.telephony.Ionlyownersimsupport

I tried to get the imei:

TelephonyManager telephonyManager = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
        if (ActivityCompat.checkSelfPermission(this, READ_PHONE_STATE) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            return;
        }
        String imei = telephonyManager.getImei();

I tried to get the name of the operator:

TelephonyManager manager = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
            String nomeOperadora = manager.getNetworkOperatorName();
            printarImei.setText(nomeOperadora);

But it always gives some error, sometimes error of permission even granting the permission in Manifest.xml... Thank you already!! Thank you!