1：AndroidManifest.xml加入权限，是否唤起拨号权限

 <uses-permission  android:name="android.permission.CALL_PHONE" />

2：布局，拨打客服按钮

 <TextView
        android:id="@+id/call"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="客服!"
        android:textColor="#fff"
        android:background="#bc5757"/>

3：代码块，特别简单

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView call = findViewById(R.id.call);
        //点击按钮拨打电话
        call.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(Intent.ACTION_CALL,Uri.parse("tel:"+"要拨打的电话号码"));
                startActivity(intent);
            }
        });

    }
}