At&t account identity theft: how do I report it?

https://www.att.com/support/article/wireless/KM1159583/

I know my account has been hacked but how do I get that person off and especially my phone #.  when I sign into Facebook I am not signing in from where I live but from 2 other states.  my mane is Kathleen, my # is 1 715 xxx xxxx. I live in Wisconsin and somehow I am signing into Facebook in Denver Co. or Kentucky. 

Kathleen, I wonder how you got hacked?  Have you ever posted personal information on a public website?