Hey Alice! I'm Amy and have four characters here - the AU!Cas, along with Anna Milton, Norman Jayden, and Dr. Meredith Grey. I've never seen/read Attack on Titan, but I've definitely heard some good things. I also had to read the wiki, but if it's any consolation, they were INTERESTING spoilers!
And yes, the communicator has a speech function XD. If someone's truly up on using it, she's welcome to do so!