Cant add phone number to iMessage

I use iphone 6 before i use my new device now. The imessage worked perfectly fine. I can use my phone number as my imessage contact. Recently, i got iphone 7, but I cant use my phone number for imessage. I dont even have option on my “send & receive” tab. I can only use my email for imessage. I already add my phone number in my apple id for contact to be reached at, but I still cant see the phone number option. What do i do? I want to use my phone number for imessage