As far as I know, only the caller can add other people to conference and not the receiver. Can you try the same when you call someone and not the other way round?
This is the new update by Samsung. It's a Rich Communication Services (RCS) messaging service. With this, Users will enjoy rich messaging features such as group chats, video calls and large file transfers, while continuing to use their phone numbers without the need for an additional app. This icon is enabled if the other person on call uses the RJIO SIM card. This is Volte SIM feature and if both the parties have RJIO SIM then only this icon will be enabled.
