Difference between “I am going to” vs. ” I was going to”

I am new here in the United States and I’m just confused how the natives speak.

I just want to know the meaning of these statements.

Sentence 1:
Ann said that she was going to Las Vegas with here boss, and the whole office was talking about it.

Sentence 2:
I was just notified that I am going to be transferred in Mongolia. We’ll see about that! I am going to talk to the boss.

What is the difference between the two?

For sentence 1, Is Ann still going to Las Vegas with her boss? When “was going to” is used, does it change the fact the Ann is going to Las Vegas? If I change was going to to am going to, Will it make any difference, will it make sense?

About the sentence 2, Why is “am going to” used? Will it change the meaning of the sentence if I change it to “was going to?”..