I'm Grace. lets chat. 

你好我叫柯雅。谈话吧

你好，我叫柯雅。（nice Chinese name~）

我们来聊天吧。

我们来：（lets） （add a 来（lái） in here beacause  make people intimate ，like we chat closer.

Chat is a relax way to talk to people，right?

谈话 is a formal usage，

just like your father talk to u about your error，

your boss talk to u about your problem these days，

the conversion between with the leaders of nation balabala.... 

So in China,we called chat is 聊天(liáo tiān)

（My English is not good,please have a look）