I'm going to bring up a TV show, a movie, and my personal experience in customer service:

In "Resident Alien" (very funny show, btw), Alan Tudyk is an alien who teaches himself how to speak like humans by watching episodes of "Law and Order" and repeating the dialogue.

In " The Room", a young woman who was kidnapped and later had a child by her kidnapper had the child repeat what he heard on TV as a way to teach him how to speak intelligibly.

As for my personal experience, just listening to how my coworkers explained things to customers over the phone, and my having to explain things over and over to customers, really helped me polish my speech.

Good luck!

ETA: corrected "the room" to "Room"