Why don't I have a merge option on my Samsung Galaxy Note Edge LtA x3?

[AC Question]

Why i does not have a merge option in samsung galacxy note edge LtA x3

I want to make a conference call but when i add a call the first call goes to hold and only i have the swap option there no option of merge soo plz help me any one what can i do to find the merge option to make a conference call thanks