Occasionally in Metal Gear Solid V: The Phantom Pain, right before a key cinematic relating to Mother Base appears, a character (either Miller or Ocelot) will give a brief call to the player giving a rough explanation for what's going on that is important enough to require the player (as Venom Snake)'s presence before the player is automatically brought back to Mother Base for the cutscene (as implied by the chopper sound effect upon the call's end).
Battle Gear proposal
Benedict "Kazuhira" Miller: Boss... About those Walker Gears spreading all over Africa, Huey's got an idea for a counterweapon. Come on back to Mother Base.
Battle Gear development
Revolver "Shalashaska" Ocelot: We've begun development on that new "Battle Gear" weapon that Emmerich was talking about. If you want to see how development's going, come take a look for yourself.
Revolver "Shalashaska" Ocelot: Boss, we have an emergency. Many of our staff are falling ill. At first, it seemed like a common cold, but before we knew it, blisters started popping up on their chests, and... Damn it... I'll fill you in at the ACC. Just get in the chopper.
This is the only pre-cinematic call that doesn't involve returning to Mother Base or a cutscene.
Battle Gear completed
A Selfless Act
Benedict "Kazuhira" Miller: Prolonged time in the field is bad for the body and mind. I think it's time you took a break. Do it for me. Come back to Mother Base ASAP.
Although the specific reason for calling him back to Mother Base is never stated in this call, it is implied in Miller's call to Big Boss shortly after the "A Selfless Act" cutscene that he called him in to inform him of the discovery of Strangelove's corpse in the AI pod.
Benedict "Kazuhira" Miller: Code Talker examined everyone here, and… one of us is infected. It’s Quiet. It was our cutting-edge MRI that finally revealed it. But we don’t know what language strain it is. Get back to base. Time for her to talk. You know the room number – “101.”
Benedict "Kazuhira" Miller: Boss, as we suspected, the mastermind behind the kids' escape was Eli. It's hard to believe, but apparently he'd been plotting an armed uprising against us. He could be hiding something else too. Ocelot's going to press him for answers. Get back here as quick as you can!
Parasite outbreak on quarantine platform
Benedict "Kazuhira" Miller: Boss, we have an emergency. There's been another outbreak of the vocal cord parasites on the base. Several men are dead. It started in the Laboratory on the Quarantine Platform, where that radiation leak occurred. I'd only just deployed the Security Team... I've sent in a rescue team to help, but they haven't returned. Boss, I need you on this. Come back to Mother Base ASAP.
Huey's trial and exile
Benedict "Kazuhira" Miller: Boss, you there? We have a problem. The staff have found out everything that Emmerich's been up to. They're right on the edge. I need you to intervene before things get out of control. Get back to Mother Base ASAP.
Benedict "Kazuhira" Miller: Boss, we have an emergency! Get back to Mother Base, right now! I mean it - hurry!