How to view/send picture text while talking on iphone

This is not true that you can "send/receive an iMessage when on a call while the iPhone is connected to an available wi-fi network". I am currently connected to my WIFI and tried to send a picture...still can't do it. I want to know how to change this feature. On my Iphone 4s, I was able to without a problem. Now that I have the SE, it won't let me..WHY? This is exactly why I didn't want to upgrade. However, the 4S was no longer able to update, and some apps would not work.

If you are in the U.S. and your carrier is Verizon or Sprint, you can't access the internet while on a call with their network. MMS with the iPhone requires cellular data. You can send/receive an iMessage when on a call while the iPhone is connected to an available wi-fi network.