I don't. But you can assign a key (paddle?) to it.
Edit: just checked - go to options -> controller -> change bindings -> then it's in the communication tab (third one).
I'd recommend binding your l4 to the select button, r4 to start, and r5 to left bumper. Makes it much easier to call in strategems and use the map during play. Use l5 to open comms then
Also change the grenade key to tap right bumper and unmap it from the right arrow d-pad button then change the right d-pad button to mark. If you don't unbind it, you'll mark and throw a grenade at the same time