Do you know that you can call up to 5 persons at the same time on your smartphone using the conference call services? With conference call services you can hold group calls with up to 5 people at once by calling the first person then keep adding up more people using the “Add Call” icon on the current call screen.
How to make a conference call on Android would be very simple if you follow the below steps.

These steps don’t require any conference call settings in android before your conference call in Android.

How To Set Up Conference Call Services On Android Phones
See below!!

http://techmila.com/how-to-use-conference-call-services-on-android/