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I am somehow the same. Through typing I feel like I can be my own self all of the time. While when it is face to face or through phone calls it's depends on who I am talking to and how much I feel comfortable with them.
I can speak as I type when I am with people who are very close to me "in real life". It is just a matter of shyness. Work on your shyness and you should speak as you write.
Maybe it also has to do with the fact that when you write you have more time to think about what you are going to say so you sound "better". You just have to practise face to face conversations I guess.