Example: If I'm using Vodafone Network it will display the service provider name that my mobile is currently using.

TelephonyManager telephonyManager = (TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);
        String deviceID =telephonyManager.getDeviceId();
        String deviceID1 =telephonyManager.getSimSerialNumber();
        String deviceID2 =telephonyManager.getSimOperatorName();

Use This code it will give you your service provider name

TelephonyManager telephonyManager = ((TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE));
String operatorName = telephonyManager.getNetworkOperatorName();

package com.example.serviceprovider;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.telephony.TelephonyManager;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.os.Build;

public class MainActivity extends ActionBarActivity {

 TextView serviceProviderTextView;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
  setContentView(R.layout.main);

  serviceProviderTextView = (TextView) findViewById(R.id.Service);

 }

 public void getServiceProvider(View view) {

  TelephonyManager manager = (TelephonyManager)
  getSystemService(Context.TELEPHONY_SERVICE);
  String carrierName = manager.getNetworkOperatorName();
  serviceProviderTextView.setText(carrierName);

 }

}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/Service"
        android:text="hello"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>


    <Button
        android:id="@+id/click"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="getServiceProvider"
        android:text="Click me"/>

</LinearLayout>