Sending Video MMS on WP8.1

Call me old fashioned for still using MMS, but I cannot for the life of me find a way to send videos as MMS on my windows phone?

On previous dumb phones I've owned, the phone automatically trimmed and compressed the videos for me, but whenever I try to MMS a video on Windows Phone it refuses to send and doesn't offer to convert, trim or compress the file.
Suggestions?

Turn on cellular and try it. That's what I had to since having my 928 on Verizon but can't remember when I had 900 or 920 on AT&T. I have an Icon now and I have to turn on cellular to send and receive pics. That's why I was wanting the cellular toggle.